Service continuity ensuring method, control plane gateway, and mobility management network element

ABSTRACT

A service continuity ensuring method, a control plane gateway, and a mobility management network element are provided. The method includes receiving, by a control plane gateway (C-GW), current location information of a user equipment (UE) sent by a mobility management network elements, selecting, by the C-GW, at least one forwarding D-GW for the UE according to the current location information of the UE, and establishing, by the C-GW for the UE, a data forwarding tunnel between a source D-GW of the UE and the forwarding D-GW, and a data forwarding tunnel between the forwarding D-GW and a target base station of the UE. The data forwarding tunnels are used to transmit uplink user plane data and/or downlink user plane data of the UE in a moving process of the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/940,348, filed Mar. 29, 2018, which is a continuation ofInternational Patent Application No. PCT/CN2015/091242, filed on Sep.30, 2015. Both of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the communications field, and morespecifically, to a service continuity ensuring method, a control planegateway, and a mobility management network element.

BACKGROUND

A distributed gateway (DGW) architecture is an enhanced networkarchitecture proposed on the basis of an existing evolved packet system(EPS) network architecture according to an idea of separating a networkcontrol plane function from a user plane function. The DGW architectureincludes a control plane gateway (C-GW) and a user plane gateway (U-GW).

The C-GW is a centralized control plane gateway, and may have two forms:(1) a single network element obtained after a control plane function ofa serving gateway (S-GW) and a control plane function of a packet datanetwork gateway (P-GW) in an existing 3^(rd) Generation PartnershipProject (3GPP) EPS network are integrated, and (2) two independentnetwork elements that separately implement a control plane function ofan existing Control Plane S-GW and a control plane function of anexisting P-GW. The C-GW is specially configured to process control planesignaling in the 3GPP EPS network, including signaling related tofunctions such as mobility management, session management, addressmanagement, path management, and accounting management. The C-GWinteracts with the U-GW to implement control and management on userplane data processing.

The U-GW is a distributed user plane gateway. Corresponding to the twoforms of the C-GW, the U-GW may also have two forms: (1) a singlenetwork element obtained after a user plane function of the S-GW and auser plane function of the P-GW in the existing 3GPP EPS network areintegrated, and (2) two independent network elements that separatelyimplement a user plane function of the existing User Plane S-GW and auser plane function of the existing User Plane P-GW. The U-GW isspecially configured to process user plane data in the 3GPP EPS network,including functions such as routing and forwarding, data packet check,data packet counting, and quality of service enforcement. The U-GWprocesses user plane data under control and management of the C-GW. Inconsideration of a feature that the U-GW can be deployed in adistributed manner, the U-GW may also be referred to as a D-GW.

In the existing EPS network architecture, service continuity isimplemented by means of an anchor function of the P-GW. That is, in amoving process of a user equipment (UE) in a connected mode thatperforms a user plane service, user plane data of the UE is alwaysexchanged between the current P-GW and an external data network. Becausethe P-GW does not change in the moving process, it is ensured that auser plane IP address does not change, to further ensure continuity ofthe user plane service.

The U-GW (or the D-GW) in the DGW architecture may be deployed in adistributed manner according to a service requirement, to implementlocal access of a user, further shorten a round trip time (RTT) of userplane data, and improve user experience. During deployment, the U-GW maybe moved downwards to a metropolitan area network closer to the user andeven to a base station controller. With downward movement of the U-GW, aservice range of the U-GW is far smaller than a service range of theS-GW/P-GW deployed in a centralized manner in the EPS network.Therefore, a probability that the serving U-GW changes in the movingprocess of the UE increases.

It may be learned that in the DGW architecture, how to ensure servicecontinuity in the moving process of the UE is a prominent problem.

SUMMARY

Embodiments of the present disclosure provide a service continuityensuring method, a control plane gateway, and a mobility managementnetwork element, to establish, for a UE, a data forwarding tunnelbetween a forwarding U-GW and a source U-GW, and a data forwardingtunnel between the forwarding U-GW and a target base station of the UE,in order to ensure service continuity in a moving process of the UE, andimprove user service experience.

According to a first aspect, a service continuity ensuring method isproposed. The method includes receiving, by a control plane gateway,current location information of a user equipment sent by a mobilitymanagement network element for the user equipment, selecting, by thecontrol plane gateway, at least one forwarding user plane gateway forthe user equipment according to the current location information of theuser equipment, and establishing, by the control plane gateway for theuser equipment, a data forwarding tunnel between a source user planegateway serving the user equipment and the forwarding user planegateway, and a data forwarding tunnel between the forwarding user planegateway and a target base station of the user equipment. The dataforwarding tunnels are used to transmit uplink user plane data and/ordownlink user plane data of the user equipment in a moving process ofthe user equipment.

According to a second aspect, a service continuity ensuring method isproposed. The method includes receiving, by a target mobility managementnetwork element, a forwarding relocation request sent by a sourcemobility management network element serving a user equipment, where theforwarding relocation request carries current location information ofthe user equipment, selecting, by the target mobility management networkelement, a target control plane gateway of the user equipment accordingto the current location information of the user equipment, and sending,by the target mobility management network element, the current locationinformation of the user equipment to the target control plane gateway,such that the target control plane gateway determines a forwarding userplane gateway of the user equipment according to the current locationinformation of the user equipment. The method further includes sending,by the target mobility management network element, a data forwardingtunnel establishment request to the target control plane gateway. Thedata forwarding tunnel establishment request is used to request thetarget control plane gateway to establish, for the user equipment, adata forwarding tunnel between the forwarding user plane gateway and asource user plane gateway serving the user equipment, and a dataforwarding tunnel between the forwarding user plane gateway and a targetbase station serving the user equipment.

According to a third aspect, a service continuity ensuring method isproposed. The method includes receiving, by a control plane gateway,current location information of a user equipment sent by a mobilitymanagement network element, selecting, by the control plane gateway, atarget user plane gateway for the user equipment according to thecurrent location information of the user equipment, and sending, by thecontrol plane gateway, a request message to the mobility managementnetwork element. The request message is used to request the mobilitymanagement network element to release a first bearer context andindicate to the user equipment to send a setup request for a secondbearer context. The first bearer context is a bearer context of the userequipment that is established on a source user plane gateway of the userequipment, and the second bearer context is a bearer context that isre-established by the user equipment on the target user plane gatewayaccording to the first bearer context.

According to a fourth aspect, a control plane gateway is proposed,including a memory, a processor, a receiver, and a transmitter. Thememory is configured to store a program, and provide data and aninstruction for the processor. The processor is configured to executethe program stored in the memory, such that when executed, the processoris configured to perform the following operations: receiving, by usingthe receiver, current location information of a user equipment sent by amobility management network element; selecting at least one forwardinguser plane gateway for the user equipment according to the currentlocation information of the user equipment; and establishing, for theuser equipment, a data forwarding tunnel between a source user planegateway serving the user equipment and the forwarding user planegateway, and a data forwarding tunnel between the forwarding user planegateway and a target base station serving the user equipment. The dataforwarding tunnels are used to transmit uplink user plane data and/ordownlink user plane data of the user equipment in a moving process ofthe user equipment.

According to an fifth aspect, a mobility management network element isproposed, including a memory, a processor, a receiver, and atransmitter. The memory is configured to store a program, and providedata and an instruction for the processor. The processor is configuredto execute the program stored in the memory, such that when executed,the processor is configured to perform the following operations:receiving, by using the receiver, a forwarding relocation request sentby a source mobility management network element serving a userequipment, where the forwarding relocation request carries currentlocation information of the user equipment; selecting a target controlplane gateway of the user equipment according to the current locationinformation of the user equipment; sending the current locationinformation of the user equipment to the target control plane gateway byusing the transmitter, such that the target control plane gatewaydetermines a forwarding user plane gateway of the user equipmentaccording to the current location information of the user equipment; andsending a data forwarding tunnel establishment request to the targetcontrol plane gateway by using the transmitter. The data forwardingtunnel establishment request is used to request the target control planegateway to establish, for the user equipment, a data forwarding tunnelbetween the forwarding user plane gateway and a source user planegateway serving the user equipment, and a data forwarding tunnel betweenthe forwarding user plane gateway and a target base station serving theuser equipment.

According to a sixth aspect, a control plane gateway is proposed,including a memory, a processor, a receiver, and a transmitter. Thememory is configured to store a program, and provide data and aninstruction for the processor. The processor is configured to executethe program stored in the memory such that when executed, the processoris configured to perform the following operations: receiving, by usingthe receiver, current location information of a user equipment sent by amobility management network element; selecting a target user planegateway for the user equipment according to the current locationinformation of the user equipment; and sending a request message to themobility management network element by using the transmitter. Therequest message is used to request the mobility management networkelement to release a first bearer context and indicate to the userequipment to send a setup request for a second bearer context. The firstbearer context is a bearer context of the user equipment that isestablished on a source user plane gateway of the user equipment, andthe second bearer context is a bearer context that is re-established bythe user equipment on the target user plane gateway according to thefirst bearer context.

According to the service continuity ensuring method, the control planegateway, and the mobility management network element in the embodimentsof the present disclosure, the control plane gateway selects theforwarding U-GW for a UE, and establishes, for the UE, the dataforwarding tunnel between the forwarding U-GW and the source U-GW, andthe data forwarding tunnel between the forwarding U-GW and the targetbase station of the UE, in order to ensure service continuity in amoving process of the UE, and improve user service experience.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly describes theaccompanying drawings required for describing the embodiments. Theaccompanying drawings in the following description show merely someembodiments of the present disclosure, and a person of ordinary skill inthe art may still derive other drawings from these accompanying drawingswithout creative efforts.

FIG. 1 is a schematic diagram of two distributed gateway networkarchitectures according to an embodiment of the present disclosure;

FIG. 2 is a flowchart of a service continuity ensuring method accordingto an embodiment of the present disclosure;

FIG. 3 is an interaction flowchart of ensuring service continuityaccording to an embodiment of the present disclosure;

FIG. 4 is another interaction flowchart of ensuring service continuityaccording to an embodiment of the present disclosure;

FIG. 5 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure;

FIG. 6A and FIG. 6B are still another interaction flowchart of ensuringservice continuity according to an embodiment of the present disclosure;

FIG. 7 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure;

FIG. 8 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure;

FIG. 9 is another flowchart of a service continuity ensuring methodaccording to an embodiment of the present disclosure;

FIG. 10 is still another flowchart of a service continuity ensuringmethod according to an embodiment of the present disclosure;

FIG. 11 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure;

FIG. 12 is a schematic structural diagram of a control plane gatewayaccording to an embodiment of the present disclosure;

FIG. 13 is another schematic structural diagram of a control planegateway according to an embodiment of the present disclosure;

FIG. 14 is a schematic structural diagram of a mobility managementnetwork element according to an embodiment of the present disclosure;

FIG. 15 is still another schematic structural diagram of a control planegateway according to an embodiment of the present disclosure;

FIG. 16 is still another schematic structural diagram of a control planegateway according to an embodiment of the present disclosure;

FIG. 17 is another schematic structural diagram of a mobility managementnetwork element according to an embodiment of the present disclosure;and

FIG. 18 is still another schematic structural diagram of a control planegateway according to an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The following clearly describes the technical solutions in theembodiments of the present disclosure with reference to the accompanyingdrawings in the embodiments of the present disclosure. The describedembodiments are some but not all of the embodiments of the presentdisclosure. All other embodiments obtained by a person of ordinary skillin the art based on the embodiments of the present disclosure withoutcreative efforts shall fall within the protection scope of the presentdisclosure.

The technical solutions of the present disclosure may be applied tovarious communications systems, such as a Global system for mobilecommunications (GSM), a Code Division Multiple Access (CDMA) system, aWideband Code Division Multiple Access (WCDMA), a general packet radioservice (GPRS), Long Term Evolution (LTE), and a fifth generation (5G)network.

In the embodiments of the present disclosure, a user equipment (UE) mayalso be referred to as a mobile terminal, and may be any one of thefollowing types. The user equipment may be static, mobile, portable,pocket-sized, handheld, computer built-in, or in-vehicle. The userequipment may include but is not limited to a station, a mobile station,a subscriber unit, a personal computer, a laptop computer, a tabletcomputer, a netbook, a cellular phone, a handheld device, a cordlessphone, a personal digital assistant (PDA), a data card, a USB plug-indevice, a mobile Wi-Fi hotspot device (MiFi Devices), wearable devicessuch as a smartwatch/smart glasses, a wireless modem, a wireless router,and a wireless local loop (WLL) station. The user equipment may bedistributed in an entire wireless network, and communicate with one ormore core networks by using a wireless access network.

A base station may be a base transceiver station (BTS) in the GSM or theCDMA, may be a NodeB in the WCDMA, or may be an evolved NodeB (eNB ore-NodeB) in the LTE. This is not limited in the present disclosure.However, for ease of description, description is provided by using theeNB as an example in the following embodiments.

A C-GW may have two forms: (1) a single network element obtained after acontrol plane function of a S-GW and a control plane function of a P-GWin an existing 3GPP EPS network are integrated, and (2) two independentnetwork elements that separately implement a control plane function ofan existing Control Plane S-GW and a control plane function of anexisting Control Plane P-GW. This is not limited in the presentdisclosure.

Corresponding to the two forms of the C-GW, a U-GW may also have twoforms: (1) a single network element obtained after a user plane functionof the S-GW and a user plane function of the P-GW in the existing 3GPPEPS network are integrated, and (2) two independent network elementsthat separately implement a user plane function of the existing UserPlane S-GW and a user plane function of the existing User Plane P-GW.This is not limited in the present disclosure. In consideration of afeature that the U-GW can be deployed in a distributed manner, the U-GWmay also be referred to as a D-GW.

Multiple U-GWs in a same service area may form one U-GW resource pool.U-GWs in one U-GW resource pool can directly communicate with eachother. One default U-GW may be configured in each U-GW resource pool, toimplement communication with a U-GW in another U-GW resource pool.

FIG. 1 is a schematic diagram of two DGW network architectures accordingto an embodiment of the present disclosure. A DGW architecture 1 isabove a dashed line, and a DGW architecture 2 is beneath the dashedline.

In the DGW architecture 1, all control plane functions of an S-GW and aP-GW in an existing EPS network architecture are integrated into a C-GW,and all user plane functions of the S-GW and the P-GW in the existingEPS network architecture are integrated into a U-GW. A new interface isintroduced between the two network elements: the C-GW and the U-GW, suchas an S18 interface, to implement communication between the C-GW and theU-GW. In the network architecture, another network element and interfacemay reuse the existing EPS network architecture. The newly added S18interface may reuse an interface protocol between the S-GW and the P-GW,such as the GTP, or another interface protocol, or a newly definedprotocol. This is not limited in this embodiment of the presentdisclosure.

In the DGW architecture 2, the S-GW and the P-GW in the existing EPSnetwork architecture are separately split into an independent controlplane functional network element and an independent user planefunctional element (an S-GW-C and an S-GW-U, and a P-GW-C and a P-GW-U).The S-GW-C and the P-GW-C may be collectively referred to as a C-GW, andthe S-GW-U and the P-GW-U may be collectively referred to as a U-GW. Anexisting interface between the S-GW and the P-GW is also split into acontrol plane interface and a user plane interface, such as an S5-Cinterface and an S5-U interface in the DGW architecture 2. A newinterface is introduced between the two network elements: the S-GW-C andthe S-GW-U, such as an S18 interface, to implement communication betweenthe S-GW-C and the S-GW-U. A new interface is introduced between the twonetwork elements: the P-GW-C and the P-GW-U, such as an S19 interface,to implement communication between the P-GW-C and the P-GW-U. In thenetwork architecture, another network element and interface may reusethe existing EPS network architecture. The newly added S18 and S19interface may reuse an interface protocol between the S-GW and the P-GW,such as the GTP, or another interface protocol, or a newly definedprotocol. This is not limited in this embodiment of the presentdisclosure.

A method and an apparatus in the embodiments of the present disclosuremay be applied to a communications system shown in the DGW architecture1 or the DGW architecture 2 in FIG. 1. For ease of description, thecommunications system shown in the DGW architecture 1 is used as anexample in the embodiments of the present disclosure. For thecommunications system shown in the DGW architecture 2, in thisembodiment of the present disclosure, the C-GW is equivalent to anintegrated network element of the S-GW-C and the P-GW-C in the DGWarchitecture 2, and the U-GW is equivalent to an integrated networkelement of the S-GW-U and the P-GW-U in the DGW architecture 2.

FIG. 2 is a flowchart of a service continuity ensuring method accordingto an embodiment of the present disclosure. The method in FIG. 2 isperformed by a control plane gateway. The method includes the followingsteps.

201. The C-GW receives current location information of a UE sent by amobility management network element.

This embodiment of the present disclosure is applicable to any one ofthe following application scenarios.

(1) During user plane data transmission, the connected-mode UE is moved,and a location area after the movement falls beyond a service range of asource base station; and after sensing that the UE is moved out of theservice range of the source base station, the source base stationdetermines to initiate a connected-mode user plane data serviceswitchover procedure. The source base station is a serving base stationused before the UE is moved to the current location area.

(2) When uplink user plane data needs to be transmitted, the idle-modeUE is moved out of a current registered location area, such as a currentregistered tracking area (TA), and the UE initiates a location updateprocedure, such as a tracking area update (TAU) procedure.

(3) When uplink user plane data needs to be transmitted, the idle-modeUE is moved out of a service area of a current serving base station butis not moved out of a current registered location area, such as acurrent registered TA, and the UE initiates a service request procedure.

In the application scenario (1), after receiving a user plane dataswitchover request sent by the source base station, the mobilitymanagement network element may send a service switchover notification tothe serving C-GW of the UE. It should be understood that the mobilitymanagement network element may be an MME or another network element thathas a mobility management function of an MME. In some implementations,the mobility management network element may send the service switchovernotification by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the service switchover notification by using a newlycreated message. A specific message used for sending the serviceswitchover notification is not limited in the present disclosure.

In the application scenario (2), after receiving a location updaterequest sent by the UE, or successfully creating a radio access bearercontext for the UE, the mobility management network element may send arequest message to the serving C-GW of the UE. It should be understoodthat the mobility management network element may be an MME or anothernetwork element that has a mobility management function of an MME. Insome implementations, the mobility management network element may sendthe request message by using an existing message such as a createsession request message, a modify bearer request message, or a modifyaccess bearer request message. Alternatively, the mobility managementnetwork element may send the request message by using a newly createdmessage. A specific message used for sending the request message is notlimited in the present disclosure.

In the application scenario (3), after receiving a service request sentby the UE, or successfully creating a radio access bearer context forthe UE, the mobility management network element may send a requestmessage to the serving C-GW of the UE. It should be understood that themobility management network element may be an MME or another networkelement that has a mobility management function of an MME. In someimplementations, the mobility management network element may send therequest message by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the request message by using a newly created message. Aspecific message used for sending the request message is not limited inthe present disclosure.

The current location information of the UE includes a tracking areaidentity (TAI) corresponding to the current location area of the UE,serving base station information corresponding to the current locationarea of the UE, and/or the like. The corresponding TAI used when the UEis moved to the current location area is a target TAI of the UE. Thecorresponding serving base station information used after the UE ismoved to the current location area is target base station information ofthe UE. The target base station information may be a target base stationidentity (ID), a target cell identifier (CI), or the like. It may beunderstood that the current location area of the UE is also referred toas a target location area of the UE, that is, a location area of the UEafter the UE is moved out of the service range of the source servingbase station. Similarly, the current location information of the UE isalso referred to as target location information of the UE.

202. The C-GW selects at least one forwarding U-GW for the UE accordingto the current location information of the UE.

In this embodiment of the present disclosure, the current location areaof the UE falls beyond a service range of a current serving U-GW of theUE, and the C-GW needs to select an appropriate forwarding U-GW for theUE according to the current location area of the UE.

203. The C-GW establishes, for the UE, a data forwarding tunnel betweena source U-GW serving the UE and the forwarding U-GW, and a dataforwarding tunnel between the forwarding U-GW and a target base stationserving the UE.

The data forwarding tunnels are used to transmit uplink user plane dataand/or downlink user plane data of the UE in a moving process of the UE.

It should be understood that the moving process of the UE includesprocedures occurring in the foregoing three application scenarios,including the service switchover procedure in the application scenario(1), the location update procedure in the application scenario (2), andthe service request procedure in the application scenario (3).

It should be understood that the target base station of the UE is a basestation that provides an access service for the UE after the UE is movedto the current location area.

It should be understood that the data forwarding tunnels are implementedby creating a user plane bearer context between the source U-GW servingthe UE and the forwarding U-GW, and a user plane bearer context betweenthe forwarding U-GW and the target base station of the UE. The userplane bearer contexts include routing information required forforwarding user plane data. For example, a user plane bearer contextcreated on the source U-GW includes routing information of theforwarding U-GW and routing information of the source base stationserving the UE, a user plane bearer context created on the forwardingU-GW includes routing information of the source U-GW and routinginformation of the target base station, and a user plane bearer contextcreated on the target base station includes the routing information ofthe forwarding U-GW. Further, the routing information may include anaddress (typically, an Internet Protocol (IP) address) and tunnelendpoint information (typically, if a GPRS tunneling protocol (GTP) isused, the tunnel endpoint information is a GTP tunnel endpointidentifier (TEID)).

It should be understood that the forwarding U-GW is the at least oneforwarding U-GW mentioned in step 202. The data forwarding tunnels thatare established by the C-GW for the UE between the source U-GW servingthe UE and the forwarding U-GW, and between the forwarding U-GW and thetarget base station of the UE are a communication path established bythe C-GW between the source U-GW, the at least one forwarding U-GW, andthe target base station, in order to establish a data forwarding tunnelbetween the two network elements from the source C-GW to the target basestation.

For example, when the at least one forwarding U-GW includes only oneU-GW: a U-GW 1, an established data forwarding tunnel path is: thesource U-GW→the U-GW 1→the target base station. When the at least oneforwarding U-GW includes two U-GWs: a U-GW 1 and a U-GW 2, where theU-GW 1 can communicate with the source U-GW, and the U-GW 2 cancommunicate with the target base station, an established data forwardingtunnel path is: the source U-GW→the U-GW 1→the U-GW 2→the target basestation. When the at least one forwarding U-GW includes three or moreU-GWs that include a U-GW 1 that can communicate with the source U-GW,and a U-GW 2 that can communicate with the target base station, anestablished data forwarding tunnel path is: the source U-GW→the U-GW 1→. . . →the U-GW 2→the target base station. Data forwarding tunnelsindicated by the U-GW 1→ . . . →the U-GW 2 are data forwarding tunnelsbetween the at least one forwarding U-GW.

In this embodiment of the present disclosure, the C-GW determines theappropriate forwarding U-GW for the UE according to the current locationinformation after the movement, and establishes the data forwardingtunnel between the forwarding U-GW and the source U-GW, and the dataforwarding tunnel between the forwarding U-GW and the target basestation of the UE, in order to ensure service continuity in a movingprocess of the UE, and improve user service experience.

Optionally, in an embodiment, the at least one forwarding U-GW includesonly one U-GW: a first U-GW, the C-GW is a serving C-GW used after theUE is moved to the current location area, the C-GW is the same as aserving C-GW used before the UE is moved to the current location area,and the mobility management network element is a serving mobilitymanagement network element used after the UE is moved to the currentlocation area. In this case, step 203 comprises: receiving, by the C-GW,a first request sent by the mobility management network element, wherethe first request carries routing information of the target base stationof the UE; sending, by the C-GW, a second request to the first U-GW,where the second request is used to request the first U-GW to establishthe data forwarding tunnel between the first U-GW and the target basestation, and the data forwarding tunnel between the first U-GW and thesource U-GW, and the second request carries the routing information ofthe target base station and routing information of the source U-GW; andsending, by the C-GW, a third request to the source U-GW, where thethird request is used to request the source U-GW to establish the dataforwarding tunnel between the source U-GW and the first U-GW, and thethird request carries routing information of the first U-GW.

It should be understood that in this embodiment, the C-GW is the same asthe serving C-GW used before the UE is moved to the current locationarea, that is, the serving C-GW does not change in the moving process ofthe UE. It should be understood that this embodiment is applicable to ascenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Certainly, it should be understood that the C-GW further receives asecond response sent by the first U-GW according to the second request,and a third response sent by the source U-GW according to the thirdrequest. The second response is used to acknowledge that the first U-GWallows establishment of the data forwarding tunnel between the firstU-GW and the target base station, and the data forwarding tunnel betweenthe first U-GW and the source U-GW. Optionally, the second response maycarry the routing information of the first U-GW, such as an IP addressand TEID information, and the third response is used to acknowledge thatthe source U-GW allows establishment of the data forwarding tunnelbetween the source U-GW and the first U-GW. After receiving the secondresponse and the third response, the C-GW may send a first response ofthe first request to the mobility management network element.

It should be noted that the first request, the second request, or thethird request in this embodiment may be sent by using an existingmessage such as a create indirect data forwarding tunnel request, or anewly defined message. This is not limited in the present disclosure.Further, the first response, the second response, or the third responsein this embodiment may be sent by using an existing message such as acreate indirect data forwarding tunnel response, or a newly definedmessage. This is not limited in the present disclosure.

In addition, it should be understood that physical implementation of atunnel is a bearer context, and the bearer context includes routinginformation of a peer end of the tunnel. A control plane gateway needsto separately send requests to two user plane gateways, to separatelycreate bearer contexts, and the bearer contexts include routinginformation of a peer end. In this way, a tunnel is established betweenthe two user plane gateways.

Optionally, in another embodiment, the at least one forwarding U-GWincludes a second U-GW and a third U-GW, the C-GW is a serving C-GW usedafter the UE is moved to the current location area, the C-GW is the sameas a serving C-GW used before the UE is moved to the current locationarea, the mobility management network element is a serving mobilitymanagement network element used after the UE is moved to the currentlocation area, and the mobility management network element is the sameas or different from a serving mobility management network element usedbefore the UE is moved to the current location area. In this case, step203 comprises: receiving, by the C-GW, a first request sent by themobility management network element, where the first request carriesrouting information of the target base station of the UE; sending, bythe C-GW, a second request to the second U-GW, where the second requestis used to request the second U-GW to establish a data forwarding tunnelbetween the second U-GW and the target base station, and a dataforwarding tunnel between the second U-GW and the third U-GW, and thesecond request carries the routing information of the target basestation and routing information of the third U-GW; sending, by the C-GW,a third request to the third U-GW, where the third request is used torequest the third U-GW to establish the data forwarding tunnel betweenthe third U-GW and the second U-GW, and a data forwarding tunnel betweenthe third U-GW and the source U-GW, and the third request carriesrouting information of the second U-GW and routing information of thesource U-GW; and sending, by the C-GW, a fourth request to the sourceU-GW, where the fourth request is used to request the source U-GW toestablish the data forwarding tunnel between the source U-GW and thethird U-GW, and the fourth request carries the routing information ofthe third U-GW.

It should be understood that in this embodiment, the C-GW is the same asthe serving C-GW used before the UE is moved to the current locationarea, that is, the serving C-GW does not change in the moving process ofthe UE. It should be understood that this embodiment is applicable to ascenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Similarly, the C-GW further receives a second response sent by thesecond U-GW according to the second request, a third response sent bythe third U-GW according to the third request, and a fourth responsesent by the source U-GW according to the fourth request. The secondresponse is used to acknowledge that the second U-GW allowsestablishment of the data forwarding tunnel between the second U-GW andthe target base station, and the data forwarding tunnel between thesecond U-GW and the third U-GW. Optionally, the second response maycarry the routing information of the second U-GW, such as an IP addressand TEID information. The third response is used to acknowledge that thethird U-GW allows establishment of the data forwarding tunnel betweenthe third U-GW and the second U-GW, and the data forwarding tunnelbetween the third U-GW and the source U-GW. Optionally, the thirdresponse may carry the routing information of the third U-GW, such as anIP address and TEID information. The fourth response is used toacknowledge that the source U-GW allows establishment of the dataforwarding tunnel between the source U-GW and the third U-GW. Afterreceiving the second response, the third response, and the fourthresponse, the C-GW may send a first response of the first request to themobility management network element.

It should be noted that the first request, the second request, the thirdrequest, or the fourth request in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelrequest, or a newly defined message. This is not limited in the presentdisclosure. Further, the first response, the second response, the thirdresponse, or the fourth response in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelresponse, or a newly defined message. This is not limited in the presentdisclosure.

The at least one forwarding U-GW determined by the C-GW may be three ormore forwarding U-GWs. The C-GW sends a data forwarding tunnelestablishment request to each forwarding U-GW, to establish dataforwarding tunnels between the source U-GW, the at least one forwardingU-GW, and the target base station. For example, the at least oneforwarding U-GW includes a U-GW 1, a U-GW 2, and a U-GW 3. The U-GW 1can communicate with the source U-GW, the U-GW 3 can communicate with atarget U-GW, and an established forwarding tunnel path is: the sourceU-GW→the U-GW 1→the U-GW 2→the U-GW 3→the target U-GW.

Optionally, in still another embodiment, the C-GW further receivesrouting information of the source U-GW of the UE that is sent by themobility management network element. The at least one forwarding U-GWincludes only one U-GW: a first U-GW, the C-GW is a serving C-GW usedafter the UE is moved to the current location area, the C-GW isdifferent from a serving C-GW used before the UE is moved to the currentlocation area, the mobility management network element is a servingmobility management network element used after the UE is moved to thecurrent location area, and the mobility management network element isthe same as or different from a serving mobility management networkelement used before the UE is moved to the current location area. Inthis case, step 203 comprises receiving, by the C-GW, a first requestsent by the mobility management network element, where the first requestcarries routing information of the target base station of the UE, andsending, by the C-GW, a second request to the first U-GW. The secondrequest is used to request the first U-GW to establish the dataforwarding tunnel between the first U-GW and the target base station,and the data forwarding tunnel between the first U-GW and the sourceU-GW, and the second request carries the routing information of thetarget base station and the routing information of the source U-GW.

It should be understood that in this embodiment, the C-GW is differentfrom the serving C-GW used before the UE is moved to the currentlocation area, that is, the serving C-GW changes in the moving processof the UE. It should be understood that this embodiment is applicable toa scenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Similarly, the C-GW further receives a second response sent by the firstU-GW according to the second request. The second response is used toacknowledge that the first U-GW allows establishment of the dataforwarding tunnel between the first U-GW and the target base station,and the data forwarding tunnel between the first U-GW and the sourceU-GW. Optionally, the second response may carry routing information ofthe first U-GW, such as an IP address and TEID information. Afterreceiving the second response, the C-GW may send a first response of thefirst request to the mobility management network element.

Certainly, it should be understood that in this embodiment of thepresent disclosure, because the serving C-GW of the UE in thisembodiment changes in the moving process of the UE, step 203 in thisembodiment is performed by a target C-GW, that is, the serving C-GW usedafter the UE is moved to the current location area. Further, the targetC-GW should further indicate to a source C-GW via the mobilitymanagement network element, to send a data forwarding tunnelestablishment request to the source U-GW; and send the routinginformation of the first U-GW to the source U-GW. The source C-GW is aserving C-GW used before the UE is moved to the current location area,and the source U-GW is a serving U-GW used before the UE is moved to thecurrent location area.

It should be noted that the first request or the second request in thisembodiment may be sent by using an existing message such as a createindirect data forwarding tunnel request, or a newly defined message.This is not limited in the present disclosure. Further, the firstresponse or the second response in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelresponse, or a newly defined message. This is not limited in the presentdisclosure.

Optionally, in still another embodiment, the C-GW further receivesrouting information of the source U-GW of the UE that is sent by themobility management network element. The at least one forwarding U-GWincludes a second U-GW and a third U-GW, the C-GW is a serving C-GW usedafter the UE is moved to the current location area, the C-GW isdifferent from a serving C-GW used before the UE is moved to the currentlocation area, the mobility management network element is a servingmobility management network element used after the UE is moved to thecurrent location area, and the mobility management network element isthe same as or different from a serving mobility management networkelement used before the UE is moved to the current location area. Inthis case, step 203 comprises: receiving, by the C-GW, a first requestsent by the mobility management network element, where the first requestcarries routing information of the target base station of the UE;sending, by the C-GW, a second request to the second U-GW, where thesecond request is used to request the second U-GW to establish a dataforwarding tunnel between the second U-GW and the target base station,and a data forwarding tunnel between the second U-GW and the third U-GW,and the second request carries the routing information of the targetbase station and routing information of the third U-GW; and sending, bythe C-GW, a third request to the third U-GW, where the third request isused to request the third U-GW to establish the data forwarding tunnelbetween the third U-GW and the second U-GW, and a data forwarding tunnelbetween the third U-GW and the source U-GW, and the third requestcarries routing information of the second U-GW and the routinginformation of the source U-GW.

It should be understood that in this embodiment, the C-GW is differentfrom the serving C-GW used before the UE is moved to the currentlocation area, that is, the serving C-GW changes in the moving processof the UE. It should be understood that this embodiment is applicable toa scenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Similarly, the C-GW further receives a second response sent by thesecond U-GW according to the second request, and a third response sentby the third U-GW according to the third request. The second response isused to acknowledge that the second U-GW allows establishment of thedata forwarding tunnel between the second U-GW and the target basestation, and the data forwarding tunnel between the second U-GW and thethird U-GW. Optionally, the second response may carry the routinginformation of the second U-GW, such as an IP address and TEIDinformation. The third response is used to acknowledge that the thirdU-GW allows establishment of the data forwarding tunnel between thethird U-GW and the second U-GW, and the data forwarding tunnel betweenthe third U-GW and the source U-GW. Optionally, the third response maycarry the routing information of the third U-GW, such as an IP addressand TEID information. After receiving the second response and the thirdresponse, the C-GW may send a first response of the first request to themobility management network element.

Certainly, it should be understood that in this embodiment of thepresent disclosure, because the serving C-GW of the UE in thisembodiment changes in the moving process of the UE, step 203 in thisembodiment is performed by a target C-GW, that is, the serving C-GW usedafter the UE is moved to the current location area. Further, the targetC-GW should further indicate to a source C-GW via the mobilitymanagement network element, to send a data forwarding tunnelestablishment request to the source U-GW, and send the routinginformation of the third U-GW to the source U-GW. The source C-GW is aserving C-GW used before the UE is moved to the current location area,and the source U-GW is a serving U-GW used before the UE is moved to thecurrent location area.

It should be noted that the first request, the second request, or thethird request in this embodiment may be sent by using an existingmessage such as a create indirect data forwarding tunnel request, or anewly defined message. This is not limited in the present disclosure.Further, the first response, the second response, or the third responsein this embodiment may be sent by using an existing message such as acreate indirect data forwarding tunnel response, or a newly definedmessage. This is not limited in the present disclosure.

Optionally, in the foregoing four embodiments of FIG. 2, when the atleast one forwarding U-GW is the first U-GW, the method further includessending, by the C-GW, the routing information of the first U-GW to thetarget base station via the mobility management network element.

Alternatively, in the foregoing four embodiments of FIG. 2, when the atleast one forwarding U-GW is the second U-GW and the third U-GW, themethod further includes sending, by the C-GW, the routing information ofthe second U-GW to the target base station via the mobility managementnetwork element.

Optionally, in the foregoing four embodiments of FIG. 2, the method mayfurther include sending, by the C-GW, a create session request to thetarget U-GW. The create session request is used to create, on the targetU-GW for the UE, a bearer context for user plane data transmission, eachcreated bearer context includes routing information (such as an IPaddress and TEID information) of the target U-GW, and the target U-GW isa serving U-GW corresponding to the current location area of the UE. Itmay be understood that the target U-GW is generally a serving U-GW thatprovides an optimal data transmission path for the UE in the currentlocation area. Further, the C-GW sends the routing information of thetarget U-GW to the target base station via the mobility managementnetwork element.

Optionally, in the foregoing four embodiments of FIG. 2, when the atleast one forwarding U-GW is the first U-GW, the first U-GW may befurther a serving U-GW selected by the C-GW for the UE according to thecurrent location information of the UE. That is, the first U-GW is atarget U-GW. In this case, the target D-GW can directly communicate withthe source D-GW, that is, the target U-GW also plays a role of theforwarding U-GW. It may be understood that, when the target U-GW cannotdirectly communicate with the source D-GW, the forwarding U-GW selectedby the C-GW is different from the target U-GW.

The following further describes the method in the embodiments of thepresent disclosure with reference to certain implementations. For easeof description, an MME is used as a mobility management network elementin the following embodiment. Certainly, in some implementations, themobility management network element may be alternatively another devicethat has a mobility management network element function. This is notlimited in this embodiment of the present disclosure.

FIG. 3 is an interaction flowchart of ensuring service continuityaccording to an embodiment of the present disclosure. In FIG. 3, asource base station is a serving base station used before UE is moved toa current location area. A target base station is a serving base stationused after the UE is moved to the current location area. A serving MMEand a serving C-GW of the UE remain unchanged before and after movementof the UE. A source U-GW is a serving U-GW used before the UE is movedto the current location area. A target U-GW is a U-GW used after the UEis moved to the current location area. A forwarding U-GW is a U-GW thatis used after the UE is moved to the current location area and used fordata service switchover. Before the service switchover, anuplink/downlink user plane data transmission path is: the UE↔the sourcebase station↔the source U-GW, that is, transmission paths indicated by adashed line L1 a and a dashed line L2 a in FIG. 3.

A service switchover procedure in this embodiment of the presentdisclosure is as follows.

S301. The source base station initiates a user plane data switchoverprocedure of the connected-mode UE.

When the source base station of the UE senses that the UE is moved outof a service range of the source base station, and the UE is performinga user plane data service, the source base station may determine toinitiate a connected-mode user plane data service switchover procedure.

S302. The source base station sends a service switchover request messageto the MME.

To be distinguished from a service switchover request message in anotherstep in this embodiment of the present disclosure, the serviceswitchover request message sent by the source base station to the MME isreferred to as a service switchover request message 1.

The source base station sends the service switchover request message 1to the current serving MME (that is, an MME in FIG. 3), and adds currentlocation information of the UE to the message. The current locationinformation of the UE includes a TAI corresponding to the currentlocation area of the UE, serving base station information correspondingto the current location area of the UE, and/or the like. Thecorresponding TAI used when the UE is moved to the current location areais a target TAI of the UE. The corresponding serving base stationinformation used after the UE is moved to the current location area istarget base station information of the UE. The target base stationinformation may be a target base station ID, a target CI, or the like.The current location area of the UE is also referred to as a targetlocation area of the UE, that is, a location area of the UE after the UEis moved out of the service range of the source serving base station.Similarly, the current location information of the UE is also referredto as target location information of the UE.

S303. The MME sends a service switchover notification message to theC-GW.

After receiving the service switchover request message 1, the servingMME of the UE learns that the UE is moved out of the service range ofthe current base station (the source base station), and then sends theservice switchover notification message to the current serving C-GW. Theservice switchover notification message carries the current locationinformation of the UE. The service switchover notification message isused to notify the C-GW that the UE needs to be handed over to a newtarget location area. The MME may reuse an existing message such as acreate session request message, a modify bearer request message, or amodify access bearer request message, and add the current locationinformation of the UE to the message. Alternatively, the MME may definea new message to send the service switchover notification message. Thisis not limited in this embodiment of the present disclosure.

S304. The C-GW determines the target U-GW and the forwarding U-GW.

After receiving the service switchover notification message sent by theMME, the C-GW may determine, according to the current locationinformation of the UE, whether a current serving U-GW (a source U-GW) ofthe UE needs to be reallocated, that is, whether the UE is moved out ofa service range of the source U-GW. It should be noted that because theC-GW stores, in real time, service area information of each U-GW in aservice range of the C-GW, the C-GW may determine, according to thecurrent location information of the UE (such as a target TAI or a targetbase station ID), whether the UE is moved out the service range of thesource U-GW.

If the UE is not moved out of the service range of the source U-GW, dataservice switchover of the UE may be implemented in the source U-GW. Forimplementation, refer to existing or later developed approaches forswitching a data service over by a U-GW or a P-GW. Details are notdescribed in this embodiment of the present disclosure.

If the C-GW determines that a serving U-GW of the UE needs to bereallocated, the C-GW selects, according to the current locationinformation of the UE, an appropriate target U-GW, to ensure that thetarget U-GW can provide an optimal data transmission path in the currentlocation area for the UE, and to reduce a transmission RTT of user planedata as much as possible.

Further, the C-GW needs to check whether the target U-GW can directlycommunicate with the source U-GW. If the target U-GW can directlycommunicate with the source U-GW, the target U-GW is a forwarding U-GW,that is, sending performed to the forwarding U-GW in all subsequentsteps is sending performed to the target U-GW. If the target U-GW cannotdirectly communicate with the source U-GW, a U-GW that can directlycommunicate with the source U-GW is selected as a forwarding U-GWaccording to the target location information of the UE. Manners ofdetermining the target U-GW and the forwarding U-GW in FIG. 4 to FIG. 6Aand FIG. 6B are similar to this manner.

It should be noted that to ensure service continuity in a specialscenario, there may be more than one forwarding U-GW. Typically, if theUE is moved to a neighboring U-GW pool, the C-GW selects a default U-GWin the neighboring U-GW pool as a forwarding U-GW (which may be referredto as a target forwarding U-GW) that communicates with the target U-GW.If the default U-GW cannot directly communicate with the source U-GWeither, further, the C-GW may select, as a forwarding U-GW (which may bereferred as a source forwarding U-GW) that communicates with the sourceU-GW, a default U-GW in a U-GW pool in which the source U-GW is located,and two forwarding U-GWs are used to ensure service continuity in themoving process of the UE.

S305. The C-GW returns a switchover notification acknowledgment messageto the MME.

The C-GW returns the switchover notification acknowledgment message tothe MME, and adds, to the message, an address and tunnel endpointinformation of the forwarding U-GW selected by the C-GW.

For example, the address of the forwarding U-GW may be an IP address ofthe forwarding U-GW. The tunnel endpoint information of the forwardingU-GW may vary according to protocols used between the MME and the C-GW.For example, when the GTP is used between the MME and the C-GW, thetunnel endpoint information of the forwarding U-GW may be a GTP TEID.

In addition, if multiple forwarding U-GWs are determined in step S304,for example, the source forwarding U-GW and the target forwarding U-GW,the C-GW may add, to the switchover notification acknowledgment message,an address and tunnel endpoint information of the target forwarding U-GWlocated in the target location area of the UE. It should be noted that,when the switchover notification acknowledgment message is returned tothe MME, an existing message may be reused, such as a create sessionresponse message, a modify bearer response message, or a modify accessbearers response message, or a new message may be defined. This is notlimited in this embodiment of the present disclosure.

S306. The MME sends a service switchover request message to the targetbase station.

To be distinguished from a service switchover request message in anotherstep in this embodiment of the present disclosure, the serviceswitchover request message sent by the MME to the target base station isreferred to as a service switchover request message 2.

The MME sends the service switchover request message 2 to the targetbase station, and forwards, to the target base station, the address andthe tunnel endpoint information of the forwarding U-GW that are sent bythe C-GW, such that an uplink data transmission path is subsequentlyhanded over to the forwarding U-GW. The address and the tunnel endpointinformation of the forwarding U-GW may be sent by using the serviceswitchover request message 2, or may be independently sent.

S307. The target base station returns a switchover requestacknowledgment message to the MME.

To be distinguished from a switchover request acknowledgment message inanother step in this embodiment of the present disclosure, and to matcha corresponding numeral identifier with that of the service switchoverrequest message corresponding to the switchover request acknowledgmentmessage, the switchover request acknowledgment message sent by thetarget base station to the MME is referred to as a switchover requestacknowledgment message 2.

After receiving the service switchover request message 2 sent by theMME, the target base station may return the switchover requestacknowledgment message 2 to the MME, and send an address (such as an IPaddress) and tunnel endpoint information (such as a GTP TEID) of thetarget base station to the MME. Similarly, the address and the tunnelendpoint information of the target base station may be sent by using theswitchover request acknowledgment message 2, or may be independentlysent.

S308. The MME sends a data forwarding tunnel establishment request tothe C-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, the dataforwarding tunnel establishment request sent by the MME to the C-GW isreferred to as a data forwarding tunnel establishment request 1.

The MME sends the data forwarding tunnel establishment request 1 to theC-GW, and sends the address and the tunnel endpoint information of thetarget base station to the C-GW, such that a downlink data transmissionpath is subsequently handed over to the target base station.

It should be noted that the data forwarding tunnel establishment requestmay be sent by reusing an existing message such as a create indirectdata forwarding tunnel request message or a modify bearer requestmessage, or a newly defined message. This is not limited in the presentdisclosure. The description is applicable to all the embodiments of thepresent disclosure.

S309. The C-GW sends a data forwarding tunnel establishment request tothe forwarding U-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment request, the data forwarding tunnelestablishment request sent by the C-GW to the forwarding U-GW isreferred to as a data forwarding tunnel establishment request 2.

The C-GW sends the data forwarding tunnel establishment request 2 to theforwarding U-GW, and sends the address and the tunnel endpointinformation of the target base station and an address and tunnelendpoint information of the source U-GW to the forwarding U-GW.

In addition, if multiple forwarding U-GWs are required in step S304, forexample, the source forwarding U-GW (that is, the third U-GW mentionedabove) and the target forwarding U-GW (that is, the second U-GWmentioned above), the C-GW should send a data forwarding tunnelestablishment request to each forwarding U-GW, and the request carriesan address and tunnel endpoint information of a peer network element.For example, a data forwarding tunnel establishment request sent to thesource forwarding U-GW carries the address and the tunnel endpointinformation of the source U-GW and the target forwarding U-GW, and adata forwarding tunnel establishment request sent to the targetforwarding U-GW carries an address and tunnel endpoint information ofthe source forwarding U-GW and the address and the tunnel endpointinformation of the target base station.

S310. The forwarding U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment response, the data forwarding tunnelestablishment response sent by the forwarding U-GW to the C-GW isreferred to as a data forwarding tunnel establishment response 2.

The forwarding U-GW returns the data forwarding tunnel establishmentresponse 2 to the C-GW, to respond to the data forwarding tunnelestablishment request 2 sent by the C-GW, and determines thatestablishment of a data forwarding tunnel between the target basestation and the forwarding U-GW and establishment of a data forwardingtunnel between the source U-GW and the forwarding U-GW are allowed.Optionally, the data forwarding tunnel establishment response 2 maycarry the address and the tunnel endpoint information of the forwardingU-GW.

If multiple forwarding U-GWs are required in step S304, the C-GW shouldsend a data forwarding tunnel establishment request to each forwardingU-GW, and correspondingly, each forwarding U-GW should return a dataforwarding tunnel establishment response, to indicate that establishmentof a data forwarding tunnel is allowed.

It should be understood that responses to data forwarding tunnelestablishment requests in the present disclosure all indicate thatestablishment of data forwarding tunnels is allowed. If there is aresponse indicating that establishment of a data forwarding tunnel isnot allowed, the method in this embodiment of the present disclosure isno longer performed. This is applicable to the following.

It should be noted that the data forwarding tunnel establishmentresponse may be sent by reusing an existing message such as a createindirect data forwarding tunnel response message or a modify bearerresponse message, or a newly defined message. This is not limited in thepresent disclosure. The description is applicable to all the embodimentsof the present disclosure.

S311. The C-GW sends a data forwarding tunnel establishment request tothe source U-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, the dataforwarding tunnel establishment request sent by the C-GW to the sourceU-GW is referred to as a data forwarding tunnel establishment request 3.

The C-GW sends the data forwarding tunnel establishment request 3 to thesource U-GW, and sends the address and the tunnel endpoint informationof the forwarding U-GW to the source U-GW.

If multiple forwarding U-GWs are determined in step S304, the C-GWsends, to the source U-GW, an address and tunnel endpoint information ofthe source forwarding U-GW located in the current location area of theUE.

S312. The source U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment response, the data forwarding tunnelestablishment response sent by the source U-GW to the C-GW is referredto as a data forwarding tunnel establishment response 3.

The source U-GW returns the data forwarding tunnel establishmentresponse 3 to the C-GW, to respond to the data forwarding tunnelestablishment request 3 sent by the C-GW, and determines thatestablishment of the data forwarding tunnel between the forwarding U-GWand the source U-GW is allowed.

S313. Establish a data forwarding tunnel between the source U-GW and theforwarding U-GW.

After an address and tunnel endpoint information of a peer U-GW areobtained, the data forwarding tunnel between the source U-GW and theforwarding U-GW is established.

Certainly, it should be understood that if multiple forwarding U-GWs aredetermined in step S304, for example, the source forwarding U-GW and thetarget forwarding U-GW, a data forwarding tunnel between the source U-GWand the source forwarding U-GW, and a data forwarding tunnel between thesource forwarding U-GW and the target forwarding U-GW arecorrespondingly established.

S314. The C-GW returns a data forwarding tunnel establishment responseto the MME.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment response, the data forwarding tunnelestablishment response sent by the C-GW to the MME is referred to as adata forwarding tunnel establishment response 1.

After the data forwarding tunnel is established between the source U-GWand the forwarding U-GW, the C-GW returns the data forwarding tunnelestablishment response 1 to the MME to notify the MME that the dataforwarding tunnel has been established and service switchover can beperformed.

S315. The MME sends a switchover command to the source base station.

The MME sends the switchover command to the source base station, and thecommand carries the address and the tunnel endpoint information of theforwarding U-GW. If multiple forwarding U-GWs are required, for example,the source forwarding U-GW and the target forwarding U-GW, the commandcarries an address and tunnel endpoint information of the sourceforwarding U-GW located in a source location area of the UE.

S316. The source base station performs a data switchover procedure.

The source base station continues to perform the existing dataswitchover procedure, hands over the UE to a target cell, and indicatesto the UE to access the target cell, and can reuse the existingswitchover procedure in a subsequent step to implement complete handoverof the UE to a target location.

In a switchover process and after the switchover is completed, anuplink/downlink user plane data transmission path changes to: the UE↔thetarget base station↔the forwarding U-GW↔the source U-GW, that is,transmission paths indicated by a dashed line L3 a, a dashed line L4 a,a dashed line L5 a, and a dashed line L6 a in FIG. 3. It should be notedthat before, during, and after the switchover, the uplink/downlink userplane data transmission path passes through the source U-GW. However,considering that both the source U-GW and the forwarding U-GW have beenmoved downwards to locations closer to the UE, the source U-GW is alsovery close to the forwarding U-GW, and therefore, an RTT of user planedata does not significantly increase. When the C-GW determines that twoor more U-GWs are used as forwarding U-GWs, data forwarding tunnel pathsof the forwarding U-GWs pass through all the forwarding U-GWs. Forexample, if the forwarding U-GW includes the target forwarding U-GW andthe source forwarding U-GW, transmission paths change to: the UE↔thetarget base station↔the target forwarding U-GW↔the source forwardingU-GW↔the source U-GW.

It should be understood that the data forwarding tunnels established inthis embodiment of the present disclosure are implemented by creating auser plane bearer context between the source U-GW serving the UE and theforwarding U-GW, and a user plane bearer context between the forwardingU-GW and the target base station of the UE. The user plane bearercontexts include routing information (for example, an address and tunnelendpoint information) required for forwarding user plane data, includingrouting information of the source U-GW, routing information of theforwarding U-GW, and routing information of the target base station.This is also applicable to another embodiment of the present disclosure.

In this embodiment of the present disclosure, the C-GW determines theforwarding U-GW according to the current location information of the UE.The data forwarding tunnel is established between the source U-GW andthe forwarding U-GW, to ensure service continuity in a moving process ofthe UE, and ensure user service experience.

FIG. 4 is another interaction flowchart of ensuring service continuityaccording to an embodiment of the present disclosure. In FIG. 4, asource base station is a serving base station used before UE is moved toa current location area. A target base station is a serving base stationused after the UE is moved to the current location area. A serving MMEand a serving C-GW of the UE remain unchanged before and after themovement of the UE. A source U-GW is a serving U-GW used before the UEis moved to the current location area. A target U-GW is a U-GW usedafter the UE is moved to the current location area. A forwarding U-GW isa U-GW that is used after the UE is moved to the current location areaand used for data service switchover. Before the service switchover, anuplink/downlink user plane data transmission path is: the UE↔the sourcebase station↔the source U-GW, that is, transmission paths indicated by adashed line L1 b and a dashed line L2 b in FIG. 4.

S401. The source base station initiates a user plane data switchoverprocedure of the connected-mode UE.

S402. The source base station sends a service switchover request messageto the MME.

S403. The MME sends a service switchover notification message to theC-GW.

S404. The C-GW determines the target U-GW and the forwarding U-GW.

For implementation of steps S401 to S404, refer to steps S301 to S304 inFIG. 3.

S405. The C-GW sends a create session request to the target U-GW.

After selecting an appropriate target U-GW, the C-GW may initiate thecreate session request to the target U-GW, in order to create, on thetarget U-GW for the UE, a bearer context for user plane datatransmission.

S406. The target U-GW sends a create session response to the C-GW.

The target U-GW creates, for the UE according to the create sessionrequest, the bearer context for user plane data transmission of the UE.Each created bearer context includes an address (such as an IP address)and tunnel endpoint information (such as a GTP TEID) of the target U-GW.

After the bearer context creation is completed, the target U-GW may sendthe create session response to the C-GW.

S407. The C-GW returns a switchover notification acknowledgment messageto the MME.

The C-GW returns the switchover notification acknowledgment message tothe MME, and adds, to the message, the address and the tunnel endpointinformation of the target U-GW selected by the C-GW.

S408. The MME sends a service switchover request message to the targetbase station.

The MME sends the service switchover request message to the target basestation, and the message carries the address and the tunnel endpointinformation of the target U-GW that are sent by the C-GW.

S409. The target base station returns a switchover requestacknowledgment message to the MME.

After receiving the service switchover request message sent by the MME,the target base station may return the switchover request acknowledgmentmessage to the MME, and send an address (such as an IP address) andtunnel endpoint information (such as a GTP TEID) of the target basestation to the MME. Similarly, the address and the tunnel endpointinformation of the target base station may be sent by using theswitchover request acknowledgment message, or may be independently sent.

S410. The MME sends a data forwarding tunnel establishment request tothe C-GW.

S411. The C-GW sends a data forwarding tunnel establishment request tothe forwarding U-GW.

S412. The forwarding U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

S413. The C-GW sends a data forwarding tunnel establishment request tothe source U-GW.

S414. The source U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

S415. Establish a data forwarding tunnel between the source U-GW and theforwarding U-GW.

S416. The C-GW returns a data forwarding tunnel establishment responseto the MME.

S417. The MME sends a switchover command to the source base station.

For implementation of steps S410 to S417, refer to steps S308 to S315 inFIG. 3.

S418. The source base station performs a data switchover procedure.

The source base station continues to perform the existing dataswitchover procedure, hands over the UE to a target cell, and indicatesto the UE to access the target cell, and can reuse the existingswitchover procedure in a subsequent step to implement complete handoverof the UE to a target location.

In a switchover process and after the switchover is completed, adownlink user plane data transmission path is: the source basestation→the source U-GW→the forwarding U-GW→the target base station→theUE, that is, transmission paths indicated by a dashed line L3 b, adashed line L4 b, a dashed line L5 b, and a dashed line L6 b in FIG. 4.In the switchover process and after the switchover is completed, anuplink user plane data transmission path is: the UE→the target basestation→the target U-GW, that is, transmission paths indicated by adashed line L7 b and a dashed line L8 b in FIG. 4.

In this embodiment of the present disclosure, the C-GW determines,according to the current location information of the UE, whether tochange a serving U-GW, and selects the forwarding U-GW according towhether the selected target U-GW can directly communicate with thesource U-GW. The data forwarding tunnel is established between thesource U-GW and the forwarding U-GW, to ensure service continuity in amoving process of the UE, and ensure user service experience. Inaddition, the C-GW directly initiates a bearer context setup request ofthe target U-GW, and notifies the target base station of routinginformation of the target U-GW via the MME, such that uplink data can bedirectly sent from the target base station to the target U-GW withoutpassing through the forwarding U-GW and the source U-GW, implementingrouting optimization of uplink data transmission.

It should be understood that interaction procedures in the embodimentsshown in FIG. 3 and FIG. 4 are applicable to a scenario in which aserving MME and a serving C-GW of UE remain unchanged before and aftermovement of the UE. If the serving MME of the UE changes but the servingC-GW does not change before and after the movement of the UE, it onlyrequires that signaling interworking is increased between a source MMEand a target MME on the basis of the solutions in the embodiments of thepresent disclosure. The signaling interworking process belongs to theexisting technology, and details are not described in the presentdisclosure.

FIG. 5 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure. In FIG.5, a source base station is a serving base station used before UE ismoved to a current location area. A target base station is a servingbase station used after the UE is moved to the current location area. Asource MME is a serving MME used before the UE is moved to the currentlocation area. A target MME is a serving MME used after the UE is movedto the current location area. A source C-GW is a serving C-GW usedbefore the UE is moved to the current location area. A target C-GW is aserving C-GW used after the UE is moved to the current location area. Asource U-GW is a serving U-GW used before the UE is moved to the currentlocation area. A target U-GW is a U-GW used after the UE is moved to thecurrent location area. A forwarding U-GW is a U-GW that is used afterthe UE is moved to the current location area and used for data serviceswitchover. Before service switchover, an uplink/downlink user planedata transmission path is: the UE↔the source base station↔the sourceU-GW, that is, transmission paths indicated by a dashed line L1 c and adashed line L2 c in FIG. 5.

A service switchover procedure in this embodiment of the presentdisclosure is as follows.

S501. The source base station initiates a user plane data switchoverprocedure of the connected-mode UE.

When the source base station of the UE senses that the UE is moved outof a service range of the source base station, and the UE is performinga user plane data service, the source base station may determine toinitiate a connected-mode user plane data service switchover procedure.

S502. The source base station sends a service switchover request messageto the source MME.

To be distinguished from a service switchover request message in anotherstep in this embodiment of the present disclosure, the serviceswitchover request message sent by the source base station to the sourceMME is referred to as a service switchover request message 1.

The source base station sends the service switchover request message 1to the current serving MME (that is, a source MME in FIG. 5), and addscurrent location information of the UE to the message. The currentlocation information of the UE includes a TAI corresponding to thecurrent location area of the UE, serving base station informationcorresponding to the current location area of the UE, and/or the like.The corresponding TAI used when the UE is moved to the current locationarea is a target TAI of the UE. The corresponding serving base stationinformation used after the UE is moved to the current location area istarget base station information of the UE. The target base stationinformation may be a target base station ID, a target CI, or the like.It may be understood that the current location area of the UE is alsoreferred to as a target location area of the UE, that is, a locationarea of the UE after the UE is moved out of the service range of thesource serving base station. Similarly, the current location informationof the UE is also referred to as target location information of the UE.

S503. The source MME sends a forwarding relocation request message tothe target MME.

The source MME determines, according to the current location informationof the UE, whether the UE is moved out of a service range of the sourceMME. If the UE is moved out of the service range of the source MME, thesource MME selects an appropriate target MME according to the currentlocation information of the UE, and sends a forwarding relocationrequest message to the target MME, and the message carries the currentlocation information of the UE. The target MME is an MME that serves theUE after the UE is moved to the current location area.

S504. The target MME determines the target C-GW.

The target MME determines, according to the current location informationof the UE, whether a current serving C-GW of the UE needs to bereallocated, that is, whether the UE is moved out of a service range ofthe source C-GW. If the serving C-GW needs to be reallocated, the targetMME selects an appropriate target C-GW according to the current locationinformation of the UE.

S505. The target MME sends a serving C-GW change notification message tothe source MME.

The target MME sends the serving C-GW change notification message to thesource MME, in order to notify the source MME that the serving C-GW ofthe UE needs to change. When the serving C-GW change notificationmessage is sent to the source MME, an existing message may be reused,for example, a change notification request message, and new indicationinformation is added to the message. Alternatively, a new message may bedefined. This is not limited in this embodiment of the presentdisclosure.

S506. The source MME sends a service switchover notification message tothe source C-GW.

To be distinguished from a service switchover notification message inanother step in this embodiment of the present disclosure, the serviceswitchover notification message sent by the source MME to the sourceC-GW is referred to as a service switchover notification message 1.

After receiving the service switchover request message 1, the servingMME (the source MME) of the UE learns that the UE is moved out of theservice range of the current base station (the source base station), andthen sends the service switchover notification message 1 to the currentserving C-GW (the source C-GW). The message carries serving C-GW changeindication information. The source MME may reuse an existing messagesuch as a create session request message, a modify bearer requestmessage, or a modify access bearer request message, to send the serviceswitchover notification message 1, and add the current locationinformation of the UE to the message. Alternatively, the source MME maydefine a new message to send the service switchover notification message1. This is not limited in this embodiment of the present disclosure.

S507. The source C-GW sends a switchover notification acknowledgment tothe source MME.

To be distinguished from a switchover request acknowledgment message inanother step in this embodiment of the present disclosure, and to matcha corresponding numeral identifier with that of the service switchoverrequest message corresponding to the switchover notificationacknowledgment message, the switchover request acknowledgment messagesent by the source C-GW to the source MME is referred to as a switchovernotification acknowledgment message 1.

After receiving the service switchover notification message 1 sent bythe source MME, the source C-GW may return the switchover notificationacknowledgment message 1 to the source MME, and the message carries anaddress (such as an IP address) and tunnel endpoint information (such asa GTP TEID) of the source U-GW.

S508. The source MME returns a C-GW change notification acknowledgmentto the target MME.

The source MME returns the C-GW change notification acknowledgment tothe target MME, and the acknowledgment carries the address (such as anIP address) and the tunnel endpoint information (such as a GTP TEID) ofthe source U-GW.

S509. The target MME sends a service switchover notification message tothe target C-GW.

To be distinguished from a service switchover notification message inanother step in this embodiment of the present disclosure, the serviceswitchover notification message sent by the target MME to the targetC-GW is referred to as a service switchover notification message 2.

The target MME sends the service switchover notification message 2 tothe target C-GW. The service switchover notification message 2 carriesthe current location information of the UE, including the target TAI,the target base station information (the base station ID), and the like.It should be noted that the service switchover notification message isused to notify the C-GW that the UE needs to be handed over to a newtarget location area (that is, the current location area of the UE). Thetarget MME may reuse an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message, to send the service switchover notificationmessage 2, and add the target location information of the UE to themessage. Alternatively, the target MME may define a new message to sendthe service switchover notification message 2. This is not limited inthis embodiment of the present disclosure.

S510. The target C-GW determines the target U-GW and the forwardingU-GW.

After learning of a switchover request, the target C-GW selects anappropriate target U-GW according to the current location information ofthe UE, to ensure that the target U-GW can provide an optimal datatransmission path in the target location for the UE, and to reduce atransmission RTT of user plane data as much as possible.

In addition, the target C-GW needs to check whether the target U-GW candirectly communicate with the source U-GW. If the target U-GW candirectly communicate with the source U-GW, the target U-GW is aforwarding U-GW, that is, sending performed to the forwarding U-GW inall subsequent steps is sending performed to the target U-GW. If thetarget U-GW cannot directly communicate with the source U-GW, the targetC-GW selects, as a forwarding U-GW according to the current locationinformation of the UE, a U-GW that can directly communicate with thesource U-GW.

It should be noted that to ensure service continuity in a specialscenario, there may be more than one forwarding U-GW. Typically, if theUE is moved to a neighboring U-GW pool, the target C-GW selects adefault U-GW in the neighboring U-GW pool as a target forwarding U-GW.If the default U-GW cannot directly communicate with the source U-GWeither, further, the target C-GW may select, as a source forwardingU-GW, a default U-GW in a U-GW pool in which the source U-GW is located,and two forwarding U-GWs are used to ensure service continuity in themoving process of the UE.

S511. The target C-GW sends a switchover notification acknowledgmentmessage to the target MME.

To be distinguished from a switchover request acknowledgment message inanother step in this embodiment of the present disclosure, and to matcha corresponding numeral identifier with that of the service switchoverrequest message corresponding to the switchover notificationacknowledgment message, the switchover request acknowledgment messagesent by the target C-GW to the target MME is referred to as a switchovernotification acknowledgment message 2.

After determining the forwarding U-GW, the target C-GW may return theswitchover notification acknowledgment message 2 to the target MMEaccording to the service switchover notification message 2 of the targetMME, and add, to the message, an address (such as an IP address) andtunnel endpoint information (such as a GTP TEID) of the forwarding U-GWselected by the target C-GW.

If there are multiple forwarding U-GWs, for example, the sourceforwarding U-GW and the target forwarding U-GW, the target C-GW may add,to the switchover notification acknowledgment message, an address andtunnel endpoint information of the target forwarding U-GW located in thecurrent location area of the UE. When sending the switchovernotification acknowledgment message to the target MME, the target C-GWmay reuse an existing message such as a create session response message,a modify bearer response message, or a modify access bearers responsemessage, or may define a new message, to send the switchovernotification acknowledgment message 2. This is not limited in thisembodiment of the present disclosure.

S512. The target MME sends a service switchover request message to thetarget base station.

To be distinguished from a service switchover request message in anotherstep in this embodiment of the present disclosure, the serviceswitchover request message sent by the target MME to the target basestation is referred to as a service switchover request message 2.

The target MME sends the service switchover request message 2 to thetarget base station, and sends the address and the tunnel endpointinformation of the forwarding U-GW to the target base station, such thatan uplink data transmission path is subsequently handed over to theforwarding U-GW.

S513. The target base station sends a switchover request acknowledgmentmessage to the target MME.

To be distinguished from a switchover request acknowledgment message inanother step in this embodiment of the present disclosure, and to matcha corresponding numeral identifier with that of the service switchoverrequest message corresponding to the switchover request acknowledgmentmessage, the switchover request acknowledgment message sent by thetarget base station to the target MME is referred to as a switchoverrequest acknowledgment message 2.

The target base station returns the switchover request acknowledgmentmessage 2, and sends an address (such as an IP address) and tunnelendpoint information (such as a GTP TEID) of the target base station tothe target MME.

S514. The target MME sends a data forwarding tunnel establishmentrequest to the target C-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, the dataforwarding tunnel establishment request sent by the target MME to thetarget C-GW is referred to as a data forwarding tunnel establishmentrequest 1.

The target MME sends the data forwarding tunnel establishment request 1to the target C-GW, and sends the address and the tunnel endpointinformation of the target base station to the C-GW, such that a downlinkdata transmission path is subsequently handed over to the target basestation.

S515. The target C-GW sends a data forwarding tunnel establishmentrequest to the forwarding U-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, the dataforwarding tunnel establishment request sent by the target C-GW to theforwarding U-GW is referred to as a data forwarding tunnel establishmentrequest 2.

The target C-GW sends the data forwarding tunnel establishment request 2to the forwarding U-GW, and sends the address and the tunnel endpointinformation of the target base station and the address and the tunnelendpoint information of the source U-GW to the forwarding U-GW.

If multiple forwarding U-GWs are required, the target C-GW should send adata forwarding tunnel establishment request to each forwarding U-GW,and the request carries an address and tunnel endpoint information of apeer network element.

S516. The forwarding U-GW returns a data forwarding tunnel establishmentresponse to the target C-GW.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tocorrespond to the data forwarding tunnel establishment requestcorresponding to the data forwarding tunnel establishment response, thedata forwarding tunnel establishment response sent by the forwardingU-GW to the target C-GW is referred to as a data forwarding tunnelestablishment response 2.

The forwarding U-GW returns the data forwarding tunnel establishmentresponse 2 to the target C-GW, to respond to the data forwarding tunnelestablishment request 2 sent by the target C-GW, and determines thatestablishment of a data forwarding tunnel between the target basestation and the forwarding U-GW and establishment of a data forwardingtunnel between the source U-GW and the forwarding U-GW are allowed.Optionally, the data forwarding tunnel establishment response 2 maycarry the address and the tunnel endpoint information of the forwardingU-GW.

If multiple forwarding D-GWs are required in step S510, the C-GW shouldsend a data forwarding tunnel establishment request to each forwardingD-GW, and correspondingly, each forwarding D-GW should return a dataforwarding tunnel establishment response, to indicate that establishmentof a data forwarding tunnel is allowed.

S517. The target C-GW returns a data forwarding tunnel establishmentresponse to the target MME.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment response, the data forwarding tunnelestablishment response sent by the target C-GW to the target MME isreferred to as a data forwarding tunnel establishment response 1.

After receiving the data forwarding tunnel establishment response 2, thetarget C-GW returns the data forwarding tunnel establishment response 1to the target MME, and determines that establishment of the dataforwarding tunnel between the target base station and the forwardingU-GW is allowed.

S518. The target MME sends a forwarding relocation response to thesource MME.

After determining that the data forwarding tunnel between the targetbase station and the forwarding U-GW can be established, the target MMEmay send the forwarding relocation response to the source MME, and theresponse carries the address and the tunnel endpoint information of theforwarding U-GW.

S519. The source MME sends a data forwarding tunnel establishmentrequest to the source C-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, the dataforwarding tunnel establishment request sent by the source MME to thesource C-GW is referred to as a data forwarding tunnel establishmentrequest 3.

The source MME sends the data forwarding tunnel establishment request 3to the source C-GW, and sends the address and the tunnel endpointinformation of the forwarding U-GW to the source C-GW.

S520. The source C-GW sends a data forwarding tunnel establishmentrequest to the source U-GW.

To be distinguished from a data forwarding tunnel establishment requestin another step in this embodiment of the present disclosure, the dataforwarding tunnel establishment request sent by the source C-GW to thesource U-GW is referred to as a data forwarding tunnel establishmentrequest 4.

The source C-GW sends the data forwarding tunnel establishment request 4to the source U-GW, and sends the address and the tunnel endpointinformation of the forwarding U-GW to the source U-GW.

S521. The source U-GW sends a data forwarding tunnel establishmentresponse to the source C-GW.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment response, the data forwarding tunnelestablishment response sent by the source U-GW to the source C-GW isreferred to as a data forwarding tunnel establishment response 4.

After receiving the data forwarding tunnel establishment request 4 sentby the source C-GW, the source U-GW may return the data forwardingtunnel establishment response 4, and determine that establishment of thedata forwarding tunnel between the forwarding U-GW and the source U-GWis allowed.

S522. Establish a data forwarding tunnel between the source U-GW and theforwarding U-GW.

After an address and tunnel endpoint information of a peer U-GW areobtained, the data forwarding tunnel between the source U-GW and theforwarding U-GW is established.

Certainly, it should be understood that if multiple forwarding U-GWs aredetermined in step S510, for example, the source forwarding U-GW and thetarget forwarding U-GW, a data forwarding tunnel between the source U-GWand the source forwarding U-GW, and a data forwarding tunnel between thesource forwarding U-GW and the target forwarding U-GW arecorrespondingly established.

S523. The source C-GW sends a data forwarding tunnel establishmentresponse to the source MME.

To be distinguished from a data forwarding tunnel establishment responsein another step in this embodiment of the present disclosure, and tomatch a corresponding numeral identifier with that of the dataforwarding tunnel establishment request corresponding to the dataforwarding tunnel establishment response, the data forwarding tunnelestablishment response sent by the source C-GW to the source MME isreferred to as a data forwarding tunnel establishment response 3.

After receiving the data forwarding tunnel establishment response 4, thesource C-GW may send the data forwarding tunnel establishment response 3to the source MME, and determine that establishment of the dataforwarding tunnel between the forwarding U-GW and the source U-GW isallowed.

S524. The source MME sends a switchover command to the source basestation.

The source MME sends the switchover command to the source base station,and the command carries the address and the tunnel endpoint informationof the forwarding U-GW.

If multiple forwarding U-GWs are required, an address and tunnelendpoint information of the source forwarding U-GW located in a sourcelocation area of the UE are carried in the switchover command.

S525. The source base station continues to perform an existing dataswitchover procedure, hands over the UE to a target cell, and indicatesto the UE to access the target cell; and subsequently reuses theexisting switchover procedure to implement complete handover of the UEto a target location.

In a switchover process and after the switchover is completed, anuplink/downlink user plane data transmission path changes to: the UE↔thetarget base station↔the forwarding U-GW↔the source U-GW, that is,transmission paths indicated by a dashed line L3 c, a dashed line L4 c,a dashed line L5 c, and a dashed line L6 c in FIG. 5. It should be notedthat before, during, and after the switchover, the uplink/downlink userplane data transmission path passes through the source U-GW. However,considering that both the source U-GW and the forwarding U-GW have beenmoved downwards to locations closer to the UE, the source U-GW is alsovery close to the forwarding U-GW, and therefore, an RTT of user planedata does not significantly increase.

In this embodiment of the present disclosure, the target C-GW determinesthe forwarding U-GW according to the current location information of theUE, and establishes the data forwarding tunnel between the source U-GWand the forwarding U-GW, to ensure service continuity in a movingprocess of the UE, and ensure user service experience.

FIG. 6A and FIG. 6B are still another interaction flowchart of ensuringservice continuity according to an embodiment of the present disclosure.In FIG. 6A and FIG. 6B, a source base station is a serving base stationused before UE is moved to a current location area. A target basestation is a serving base station used after the UE is moved to thecurrent location area. A source MME is a serving MME used before the UEis moved to the current location area. A target MME is a serving MMEused after the UE is moved to the current location area. A source C-GWis a serving C-GW used before the UE is moved to the current locationarea. A target C-GW is a serving C-GW used after the UE is moved to thecurrent location area. A source U-GW is a serving U-GW used before theUE is moved to the current location area. A target U-GW is a U-GW usedafter the UE is moved to the current location area. A forwarding U-GW isa U-GW that is used after the UE is moved to the current location areaand used for data service switchover. Before service switchover, anuplink/downlink user plane data transmission path is: the UE↔the sourcebase station↔the source U-GW, that is, transmission paths indicated by adashed line L1 d and a dashed line L2 d in FIG. 6A and FIG. 6B.

A service switchover procedure in this embodiment of the presentdisclosure is as follows.

S601. The source base station initiates a user plane data switchoverprocedure of the connected-mode UE.

S602. The source base station sends a service switchover requestmessage.

S603. The source MME sends a forwarding relocation request message.

S604. The target MME determines the target C-GW.

S605. The target MME sends a serving C-GW change notification message tothe source MME.

S606. The source MME sends a service switchover notification message tothe source C-GW.

S607. The source C-GW sends a switchover notification acknowledgment tothe source MME.

S608. The source MME returns a C-GW change notification acknowledgmentto the target MME.

S609. The target MME sends a service switchover notification message tothe target C-GW.

S610. The target C-GW determines the target U-GW and the forwardingU-GW.

For implementation of steps S601 to S610, refer to steps S501 to S510 inFIG. 5.

S611. The target C-GW sends a create session request to the target U-GW.

After selecting an appropriate target U-GW, the target C-GW may initiatethe create session request to the target U-GW, in order to create, onthe target U-GW for the UE, a bearer context for user plane datatransmission.

S612. The target U-GW sends a create session response to the targetC-GW.

The target U-GW creates, for the UE according to the create sessionrequest, the bearer context for user plane data transmission of the UE.Each created bearer context includes an address (such as an IP address)and tunnel endpoint information (such as a GTP TEID) of the target U-GW.

After bearer context creation is completed, the target U-GW may send thecreate session response to the target C-GW.

S613. The target C-GW sends a switchover notification acknowledgmentmessage to the target MME.

To be distinguished from a switchover request acknowledgment message inanother step in this embodiment of the present disclosure, and to matcha corresponding numeral identifiers with that of the service switchoverrequest message corresponding to the switchover notificationacknowledgment message, the switchover request acknowledgment messagesent by the target C-GW to the target MME is referred to as a switchovernotification acknowledgment message 2.

After determining the forwarding U-GW, the target C-GW may return theswitchover notification acknowledgment message 2 to the target MMEaccording to the service switchover notification message 2 of the targetMME, and add, to the message, an address (such as an IP address) andtunnel endpoint information (such as a GTP TEID) of the target U-GWselected by the target C-GW.

S614. The target MME sends a service switchover request message to thetarget base station.

To be distinguished from a service switchover request message in anotherstep in this embodiment of the present disclosure, the serviceswitchover request message sent by the target MME to the target basestation is referred to as a service switchover request message 2.

The target MME sends the service switchover request message 2 to thetarget base station, and the message carries the address and the tunnelendpoint information of the target U-GW that are sent by the targetC-GW.

S615. The target base station sends a switchover request acknowledgmentmessage to the target MME.

To be distinguished from a switchover request acknowledgment message inanother step in this embodiment of the present disclosure, and to matcha corresponding numeral identifier with that of the service switchoverrequest message corresponding to the switchover request acknowledgmentmessage, the switchover request acknowledgment message sent by thetarget base station to the target MME is referred to as a switchoverrequest acknowledgment message 2.

The target base station returns the switchover request acknowledgmentmessage 2, and sends an address (such as an IP address) and tunnelendpoint information (such as a GTP TEID) of the target base station tothe target MME.

S616. The target MME sends a data forwarding tunnel establishmentrequest to the target C-GW.

S617. The target C-GW sends a data forwarding tunnel establishmentrequest to the forwarding U-GW.

S618. The forwarding U-GW returns a data forwarding tunnel establishmentresponse to the target C-GW.

S619. The target C-GW returns a data forwarding tunnel establishmentresponse to the target MME.

S620. The target MME sends a forwarding relocation response to thesource MME.

S621. The source MME sends a data forwarding tunnel establishmentrequest to the source C-GW.

S622. The source C-GW sends a data forwarding tunnel establishmentrequest to the source U-GW.

S623. The source U-GW sends a data forwarding tunnel establishmentresponse to the source C-GW.

S624. Establish a data forwarding tunnel between the source U-GW and theforwarding U-GW.

S625. The source C-GW sends a data forwarding tunnel establishmentresponse to the source MME.

S626. The source MME sends a switchover command to the source basestation.

For implementation of steps S616 to S626, refer to steps S514 to S524 inFIG. 5.

S627. The source base station continues to perform an existing dataswitchover procedure, hands over the UE to a target cell, and indicatesto the UE to access the target cell; and subsequently reuses theexisting switchover procedure to implement complete handover of the UEto a target location.

In a switchover process and after the switchover is completed, adownlink user plane data transmission path is: the source basestation→the source U-GW→the forwarding U-GW→the target base station→theUE, that is, transmission paths indicated by a dashed line L3 d, adashed line L4 d, a dashed line L5 d, and a dashed line L6 d in FIG. 6Aand FIG. 6B. In a switchover process and after the switchover iscompleted, an uplink user plane data transmission path is: the UE→thetarget base station→the target U-GW, that is, transmission pathsindicated by a dashed line L7 d and a dashed line L8 d in FIG. 6A andFIG. 6B.

In this embodiment of the solution of the present disclosure, the targetC-GW determines, according to the current location information of theUE, whether to change a serving U-GW, and selects the forwarding U-GWaccording to whether the selected target U-GW can directly communicatewith the source U-GW. The data forwarding tunnel is established betweenthe source U-GW and the forwarding U-GW, to ensure service continuity ina moving process of the UE, and ensure user service experience. Inaddition, the C-GW directly initiates a bearer context setup request ofthe target U-GW, and notifies the target base station of routinginformation of the target U-GW via the MME, such that uplink data can bedirectly sent from the target base station to the target U-GW withoutpassing through the forwarding U-GW and the source U-GW, implementingrouting optimization of uplink data transmission.

It should be understood that interaction procedures in the embodimentsshown in FIG. 5, FIG. 6A, and FIG. 6B are applicable to a scenario inwhich a serving MME and a serving C-GW of UE both change before andafter the movement of the UE. If the serving C-GW of the UE changes butthe serving MME does not change before and after the movement of the UE,it only requires that signaling interworking decreases between a sourceMME and a target MME on the basis of the solutions in the embodiments ofthe present disclosure. Details are not described in the presentdisclosure.

FIG. 7 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure. In FIG.7, a target base station is a serving base station used when UE switchesfrom an idle mode to a connected mode in a current location area. Asource U-GW is a serving U-GW used before the UE is moved to the currentlocation area. A target U-GW is a serving U-GW used when the UE switchesfrom the idle mode to the connected mode in the current location area. Aforwarding U-GW is a U-GW that is used after the UE is moved to thecurrent location area and used for data service switchover. An MME is aserving MME used when the UE switches from the idle mode to theconnected mode in the current location area. A C-GW is a serving C-GWused when the UE switches from the idle mode to the connected mode inthe current location area.

A procedure in this embodiment of the present disclosure is as follows.

S701. The idle-mode UE needs to send uplink user plane data.

S702. The UE sends a signaling request to the MME.

If the idle-mode UE is moved out of a current registered location area(such as a current registered TA), the UE may send the signaling requestto the MME to initiate a location update procedure. For example, if thelocation update procedure is a TAU procedure, the signaling request is alocation update request message.

If the idle-mode UE is moved out of a service area of a current servingbase station but is not moved out of a current registered location area(such as a current registered TA), the UE may send the signaling requestto the MME to initiate a service request procedure, and the signalingrequest is a service request message.

In some embodiments, the UE may send the signaling request message tothe serving MME by using the target base station, and the target basestation sends current location information of the UE to the MME.

The current location information of the UE includes a TAI correspondingto the current location area of the UE, serving base station informationcorresponding to the current location area of the UE, and/or the like.The corresponding TAI used when the UE is moved to the current locationarea is a target TAI of the UE. The corresponding serving base stationinformation used when the UE is moved to the current location area istarget base station information of the UE. The target base stationinformation may be a target base station ID, a target CI, or the like.The current location area of the UE is also referred to as a targetlocation area of the UE, that is, a location area in which the UE islocated after the UE is moved out of a service range of a source servingbase station. Similarly, the current location information of the UE isalso referred to as target location information of the UE.

S703. The MME sends a request message to the C-GW, and adds currentlocation information of the UE to the request message.

After receiving a location update request message or a service requestmessage, the serving MME of the UE learns, according to the currentlocation information of the UE, that the UE is moved out of the servicerange of the current base station (the source base station), the servingMME of the UE sends the request message to the current serving C-GW. Therequest message is used to indicate to the C-GW to move the UE to a newtarget location area. The MME may reuse an existing message such as acreate session request message, a modify bearer request message, or amodify access bearer request message, or may define a new message. Thisis not limited in this embodiment of the present disclosure.

S704. The C-GW determines the target U-GW and the forwarding U-GW.

After receiving the request message sent by the MME, the C-GW maydetermine the target U-GW and the forwarding U-GW according to thecurrent location information of the UE. For implementation, refer tostep S304 in the embodiment shown in FIG. 3. Details are not describedherein again.

S705. The C-GW returns a request acknowledgment message to the MME.

The C-GW returns the request acknowledgment message to the MME. Forimplementation, refer to step S305 in the embodiment shown in FIG. 3.Details are not described herein again.

S706. The MME sends an initial context setup request message to thetarget base station.

The MME sends the initial context setup request message to the targetbase station, and forwards, to the target base station, an address andtunnel endpoint information of the forwarding U-GW that are sent by theC-GW, such that an uplink data transmission path is subsequently handedover to the forwarding U-GW.

S707. The target base station returns an initial context setup responsemessage to the MME.

The target base station returns the initial context setup responsemessage to the MME, and sends an address (such as an IP address) andtunnel endpoint information (such as a GTP TEID) of the target basestation to the MME.

S708. The MME sends a modify bearer request message to the C-GW.

The MME sends the modify bearer request message to the C-GW, and sendsthe address and the tunnel endpoint information of the target basestation to the C-GW, such that a downlink data transmission path issubsequently handed over to the target base station. Optionally, in thisstep, the MME may send, to the C-GW, a modify access bearer requestmessage that carries the address and the tunnel endpoint information ofthe target base station.

S709. The C-GW sends a data forwarding tunnel establishment request tothe forwarding U-GW.

S710. The forwarding U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

S711. The C-GW sends a data forwarding tunnel establishment request tothe source U-GW.

S712. The source U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

S713. Establish a data forwarding tunnel between the source U-GW and theforwarding U-GW.

For implementation of steps S709 to S713, refer to steps S309 to S313 inthe embodiment shown in FIG. 3. Details are not described herein again.

S714. The C-GW returns a modify bearer response to the MME.

Optionally, corresponding to step S708, the C-GW may return a modifyaccess bearers response message to the MME.

In the location update procedure or the service request procedure, anuplink/downlink user plane data transmission path changes to: the UE↔thetarget base station↔the forwarding U-GW↔the source U-GW, that is,transmission paths indicated by a dashed line L1 e, a dashed line L2 e,and a dashed line L3 e in FIG. 7. It should be noted that theuplink/downlink user plane data transmission path passes through thesource U-GW. However, considering that both the source U-GW and theforwarding U-GW have been moved downwards to locations closer to the UE,the source U-GW is also very close to the forwarding U-GW, andtherefore, an RTT of user plane data does not significantly increase.When the C-GW determines that two or more U-GWs are used as forwardingU-GWs, data forwarding tunnel paths of the forwarding U-GWs pass throughall the forwarding U-GWs. For example, if the forwarding U-GW includesthe target forwarding U-GW and the source forwarding U-GW, transmissionpaths change to: the UE↔the target base station↔the target forwardingU-GW↔the source forwarding U-GW↔the source U-GW.

In this embodiment of the present disclosure, the C-GW determines theforwarding U-GW according to the current location information of the UE.The data forwarding tunnel is established between the source U-GW andthe forwarding U-GW, to ensure service continuity in a moving process ofthe UE, and ensure user service experience.

FIG. 8 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure. In FIG.8, a target base station is a serving base station used when UE switchesfrom an idle mode to a connected mode in a current location area. Asource U-GW is a serving U-GW used before the UE is moved to the currentlocation area. A target U-GW is a serving U-GW used when the UE switchesfrom the idle mode to the connected mode in the current location area. Aforwarding U-GW is a U-GW that is used after the UE is moved to thecurrent location area and used for data service switchover. An MME is aserving MME used when the UE switches from the idle mode to theconnected mode in the current location area. A C-GW is a serving C-GWused when the UE switches from the idle mode to the connected mode inthe current location area.

A procedure in this embodiment of the present disclosure is as follows.

S801. The idle-mode UE needs to send uplink user plane data.

S802. The UE sends a signaling request to the MME.

For implementation of step S802, refer to step S702 in FIG. 7. Detailsare not described herein again.

S803. The MME sends an initial context setup request message to thetarget base station.

The MME sends the initial context setup request message to the targetbase station. This step is an existing step in an existing locationupdate procedure or service request procedure. Therefore, herein, theMME sends an address and tunnel endpoint information of the source U-GWto the target base station.

S804. The target base station returns an initial context setup responsemessage to the MME.

The target base station returns the initial context setup responsemessage to the MME, and sends an address (such as an IP address) andtunnel endpoint information (such as a GTP TEID) of the target basestation to the MME.

S805. The MME sends a modify bearer request message to the C-GW.

The MME sends the modify bearer request message to the C-GW, and sendsthe current location information of the UE and the address and thetunnel endpoint information of the target base station to the C-GW.Optionally, in this step, the MME may send, to the C-GW, a modify accessbearer request message that carries the current location information ofthe UE and the address and the tunnel endpoint information of the targetbase station.

S806. The C-GW determines the target U-GW and the forwarding U-GW.

After receiving the modify bearer request message sent by the MME, theC-GW may determine the target U-GW and the forwarding U-GW according tothe current location information of the UE. For implementation, refer tostep S304 in the embodiment shown in FIG. 3. Details are not describedherein again.

S807. The C-GW sends a data forwarding tunnel establishment request tothe forwarding U-GW.

S808. The forwarding U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

S809. The C-GW sends a data forwarding tunnel establishment request tothe source U-GW.

S810. The source U-GW returns a data forwarding tunnel establishmentresponse to the C-GW.

S811. Establish a data forwarding tunnel between the source U-GW and theforwarding U-GW.

For implementation of steps S807 to S811, refer to steps S309 to S313 inthe embodiment shown in FIG. 3. Details are not described herein again.

S812. The C-GW returns a modify bearer response to the MME.

The C-GW returns the modify bearer response message to the MME, andsends an address and tunnel endpoint information of the determinedforwarding U-GW to the MME. Optionally, corresponding to step S805, theC-GW may return, to the MME, a modify access bearers response message,and the message carries an address and tunnel endpoint information ofthe forwarding U-GW.

S813. The MME sends a UE context modification request to the target basestation.

The MME sends the UE context modification request message to the targetbase station, and adds the address and the tunnel endpoint informationof the forwarding U-GW to the message, such that an uplink user planedata transmission path is subsequently handed over to the forwardingU-GW. It should be noted that this step is a newly added step to theexisting location update procedure or service request procedure.

S814. The target base station returns a UE context modification responsemessage to the MME.

The target base station returns the UE context modification responsemessage to the MME.

In the location update procedure or the service request procedure, anuplink/downlink user plane data transmission path changes to: the UE↔thetarget base station↔the forwarding U-GW↔the source U-GW, that is,transmission paths indicated by a dashed line L1 f, a dashed line L2 f,and a dashed line L3 f in FIG. 8. It should be noted that theuplink/downlink user plane data transmission path passes through thesource U-GW. However, considering that both the source U-GW and theforwarding U-GW have been moved downwards to locations closer to the UE,the source U-GW is also very close to the forwarding U-GW, andtherefore, an RTT of user plane data does not significantly increase.When the C-GW determines that two or more U-GWs are used as forwardingU-GWs, data forwarding tunnel paths of the forwarding U-GWs pass throughall the forwarding U-GWs. For example, if the forwarding U-GW includesthe target forwarding U-GW and the source forwarding U-GW, transmissionpaths change to: the UE↔the target base station↔the target forwardingU-GW↔the source forwarding U-GW↔the source U-GW.

In this embodiment of the present disclosure, the C-GW determines theforwarding U-GW according to the current location information of the UE.The data forwarding tunnel is established between the source U-GW andthe forwarding U-GW, to ensure service continuity in a moving process ofthe UE, and ensure user service experience.

FIG. 9 is another flowchart of a service continuity ensuring methodaccording to an embodiment of the present disclosure. The method in FIG.9 is performed by a target mobility management network element. Themethod includes the following steps.

901. The target mobility management network element receives aforwarding relocation request sent by a source mobility managementnetwork element serving a UE.

The forwarding relocation request carries current location informationof the UE.

For implementation of step 901, refer to step S503 in FIG. 5 or stepS603 in FIG. 6A and FIG. 6B.

In an application scenario in this embodiment of the present disclosure,when the UE performs service communication, a location area aftermovement falls beyond a service range of the source mobility managementnetwork element (such as an MME). The source mobility management networkelement is a serving mobility management network element used before theUE is moved to the current location area.

902. The target mobility management network element selects a targetC-GW of the UE according to current location information of the UE.

For implementation of step 902, refer to step S504 in FIG. 5 or stepS604 in FIG. 6A and FIG. 6B.

903. The target mobility management network element sends the currentlocation information of the UE to the target C-GW, such that the targetC-GW determines a forwarding U-GW of the UE according to the currentlocation information of the UE.

For implementation of step 902, refer to step S509 in FIG. 5 or stepS609 in FIG. 6A and FIG. 6B.

S904. The target mobility management network element sends a dataforwarding tunnel establishment request to the target C-GW.

The data forwarding tunnel establishment request is used to request thetarget control plane gateway to establish, for the user equipment, adata forwarding tunnel between the forwarding U-GW and a source U-GWserving the user equipment, and a data forwarding tunnel between theforwarding U-GW and a target base station serving the user equipment.

For implementation of step 904, refer to step S514 in FIG. 5 or stepS616 in FIG. 6A and FIG. 6B.

In this embodiment of the present disclosure, after the UE is moved outof the service range of the source mobility management network element,the target mobility management network element determines the targetC-GW of the UE according to the current location information of the UE,and further establishes a data forwarding tunnel between the source U-GWand the target base station of the UE for the UE by using the targetC-GW, in order to ensure service continuity in a moving process of theUE, and improve user service experience.

Optionally, in an embodiment, the target C-GW is different from aserving C-GW used before the UE is moved to the current location area(that is, the serving C-GW changes in the moving process of the UE). Inthis case, after step 902 and before step 903, the method may furtherinclude sending, by the target mobility management network element, achange notification message to the source mobility management networkelement, where the change notification message is used to indicate thata serving C-GW of the UE changes to the target C-GW. For implementation,refer to step S505 in FIG. 5 or step S605 in FIG. 6A and FIG. 6B.

Further, before step 903, the method may further include receiving, bythe target mobility management network element, an acknowledgmentmessage sent by the source mobility management network element accordingto the change notification message. The acknowledgment message carriesrouting information of the source U-GW of the UE. For implementation,refer to step S508 in FIG. 5 or step 608 in FIG. 6A and FIG. 6B.

In this embodiment of the present disclosure, for implementation of themobility management network element, refer to the method performed bythe target MME shown in FIG. 5 or FIG. 6A and FIG. 6B. Details are notdescribed in this embodiment of the present disclosure again.

FIG. 10 is still another flowchart of a service continuity ensuringmethod according to an embodiment of the present disclosure. The methodin FIG. 10 is performed by a C-GW. The method includes the followingsteps.

1001. The C-GW receives current location information of a UE sent by amobility management network element.

This embodiment of the present disclosure is applicable to any one ofthe following application scenarios.

During user plane data transmission, the connected-mode UE is moved, anda location area after the movement falls beyond a service range of asource base station; and after sensing that the UE is moved out of theservice range of the source base station, the source base stationdetermines to initiate a connected-mode user plane data serviceswitchover procedure. The source base station is a serving base stationused before the UE is moved to the current location area.

When uplink user plane data needs to be transmitted, the idle-mode UE ismoved out of a current registered location area, such as a currentregistered TA, and the UE initiates a location update procedure, such asa TAU procedure.

When uplink user plane data needs to be transmitted, the idle-mode UE ismoved out of a service area of a current serving base station but is notmoved out of a current registered location area, such as a current TA,and the UE initiates a service request procedure.

In the application scenario (1), after receiving a user plane dataswitchover request sent by the source base station, the mobilitymanagement network element may send a service switchover notification tothe serving C-GW of the UE. It should be understood that the mobilitymanagement network element may be an MME or another network element thathas a mobility management function of an MME. In some implementations,the mobility management network element may send the service switchovernotification by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the service switchover notification by using a newlycreated message. A specific message used for sending the serviceswitchover notification is not limited in the present disclosure.

In the application scenario (2), after receiving a location updaterequest sent by the UE, or successfully creating a radio access bearercontext for the UE, the mobility management network element may send arequest message to the serving C-GW of the UE. It should be understoodthat the mobility management network element may be an MME or anothernetwork element that has a mobility management function of an MME. Insome implementations, the mobility management network element may sendthe request message by using an existing message such as a createsession request message, a modify bearer request message, or a modifyaccess bearer request message. Alternatively, the mobility managementnetwork element may send the request message by using a newly createdmessage. A specific message used for sending the request message is notlimited in the present disclosure.

In the application scenario (3), after receiving a service request sentby the UE, or successfully creating a radio access bearer context forthe UE, the mobility management network element may send a requestmessage to the serving C-GW of the UE. It should be understood that themobility management network element may be an MME or another networkelement that has a mobility management function of an MME. In someimplementations, the mobility management network element may send therequest message by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the request message by using a newly created message. Aspecific message used for sending the request message is not limited inthe present disclosure.

It should be noted that the C-GW is a C-GW serving the UE.

It should be noted that the mobility management network element is amobility management network element serving the UE. In someimplementations, the mobility management network element may be an MMEor another network element that has a mobility management function of anMME.

1002. The C-GW selects a target U-GW for the UE according to the currentlocation information of the UE.

1003. The C-GW sends a request message to the mobility managementnetwork element.

The request message is used to request the mobility management networkelement to release a first bearer context and indicate to the UE to senda setup request for a second bearer context, the first bearer context isa bearer context of the UE that is established on a source U-GW of theUE, and the second bearer context is a bearer context that isreestablished by the UE on the target U-GW according to the first bearercontext.

Optionally, in an embodiment, the request message is a delete bearerrequest message, the delete bearer request message carries areactivation request indication, and the reactivation request indicationis used to indicate, by using the mobility management network element,to the UE to initiate the setup request for the second bearer contextafter the first bearer context is deleted.

It should be understood that both the MME and the UE record the firstbearer context created by the UE on the source U-GW. After receiving thedelete bearer request message, the MME deletes the first bearer contexton the MME, and indicates to the UE to delete the first bearer contexton the UE. When the delete bearer request message carries thereactivation request indication, the MME further sends the reactivationrequest indication to the UE, to indicate to the UE to resend a setuprequest for a bearer context according to content of the first bearercontext after the first bearer context is deleted, and request to createthe second bearer context. The second bearer context is a bearer contextthat is created on the target U-GW according to the first bearercontext. Typically, the second bearer context includes an access pointname (APN) the same as that of the first bearer context.

In this embodiment of the present disclosure, before the UE changes froman idle mode to a connected mode and sends user plane data, the C-GWdetermines a serving U-GW of the UE according to the current locationinformation of the UE, triggers a bearer context deactivation procedure,and adds a reactivation request indication during the bearer contextdeactivation procedure to indicate to the UE to initiate a bearercontext recreation procedure, to recreate bearer resources on the targetU-GW, ensure service continuity of subsequent user plane datatransmission, and ensure user service experience.

The following further describes the method in the embodiments of thepresent disclosure with reference to certain implementations.

FIG. 11 is still another interaction flowchart of ensuring servicecontinuity according to an embodiment of the present disclosure. In FIG.11, a target base station is a serving base station used when UEswitches from an idle mode to a connected mode in a current locationarea. A target U-GW is a serving U-GW used when the UE switches from theidle mode to the connected mode in the current location area. An MME isa serving MME used when the UE switches from the idle mode to theconnected mode in the current location area. A C-GW is a serving C-GWused when the UE switches from the idle mode to the connected mode inthe current location area.

A procedure in this embodiment of the present disclosure is as follows.

S1101. The UE sends a signaling request to the MME.

Because the idle-mode UE needs to transmit uplink signaling or data, theidle-mode UE sends signaling to the MME, to request to switch to theconnected mode. The UE initiates a service request procedure or a TAUprocedure to implement switchover from the idle mode to the connectedmode.

In a process of switching from the idle mode to the connected mode, thetarget base station, that is, a current serving base station of the UE,reports current location information of the UE to the current servingMME, and the current location information of the UE may be a current TAIand/or a current CI.

S1102. The MME sends a location update notification message to the C-GW.

After receiving the signaling request sent by the UE for switchover fromthe idle mode to the connected mode, for example, a service requestmessage or a TAU request message, the MME determines, according to thecurrent location information of the UE reported by the base station,whether a location of the UE changes.

If the location of the UE does not change, an existing or laterdeveloped approach may be performed. Details are not described in thisembodiment of the present disclosure. If the location of the UE changes,the MME sends a location update notification message to the C-GW of theUE. Herein, the MME may determine, in the following two scenarios,whether the location of the UE changes.

(a) If the serving MME does not change, the MME may compare previouslystored location information of the UE with the current locationinformation reported by the target base station, to determine a changeof the location of the UE.

(b) If the MME changes, that is, a new MME receives the signalingrequest in the step, the new MME may consider that the location of theUE changes.

The MME sends a location update notification message to the servingC-GW, and the notification message carries the current locationinformation of the UE, including a current TAI, a current cellidentifier, and/or the like. The location update notification message isused to notify the C-GW that the current location area of the UEchanges. Therefore, the MME may reuse an existing message such as acreate session request message, a modify bearer request message, or amodify access bearer request message, to carry the current locationinformation of the UE, or may define a new message to carry the currentlocation information of the UE. This is not limited in the presentdisclosure.

In addition, the MME may determine, according to the current locationinformation of the UE, whether a serving C-GW of the UE needs to bereallocated, that is, whether the UE is moved out of a service area ofthe current serving C-GW. If the serving C-GW needs to be reallocated,the MME selects a new C-GW as a serving C-GW according to the currentlocation information of the UE, and sends a location update notificationmessage to the new C-GW. Additionally, the MME may request the new C-GWto recreate a bearer context for the UE.

S1103. The C-GW determines a U-GW.

The C-GW determines, according to the current location information ofthe UE, whether a current serving U-GW of the UE needs to bereallocated. If the current serving U-GW of the UE needs to bereallocated, the C-GW selects an appropriate target U-GW according tothe current location information of the UE, and performs step S1104. Ifthe C-GW is reallocated in S1102, generally, the serving U-GW also needsto be reallocated.

S1104. The C-GW sends a delete bearer request to the MME.

After sending the delete bearer request to the MME, the C-GW initiates abearer deactivation procedure to the UE, to release all bearer contextresources created by the UE on a source U-GW. In addition, the deletebearer request message carries a reactivation request indication, inorder to request the UE to immediately initiate a packet data network(PDN) connection establishment request after all the bearer contextresources of the source D-GW are deleted, to recreate user plane bearerresources on the target D-GW.

S1105. The MME sends a detach request or a deactivate bearer contextrequest to the UE.

After receiving the delete bearer request of the C-GW, the MME performsdifferent actions according to current PDN connection information of theUE as set forth below.

(a) If the UE currently has only one PDN connection, the MME initiates adetach procedure to the UE, and adds a reattach (re-attach required)indication to a detach request.

(b) If the UE currently has multiple PDN connections, the MME initiatesa PDN connection deactivation procedure to the UE, and adds areactivation request (Reactivation requested) indication to a deactivatebearer context request.

S1106. The UE initiates a PDN connection establishment request.

The UE initiates the PDN connection establishment request, to recoverbearer contexts that the C-GW requests to delete in step S1104. The PDNconnection establishment request carries a same APN as the bearercontexts that the C-GW requests to delete in step S1104. In thisprocedure, the C-GW uses the selected target D-GW to create a bearercontext of the UE.

If the UE receives the detach request sent by the MME in step S1105, anattach procedure is initiated, and a PDN connection establishmentprocedure is added to the attach procedure. For implementation, refer toexisting or later developed approaches.

If the UE receives the deactivate bearer context request in step S1105to deactivate a PDN connection, a separate PDN connection establishmentprocedure is initiated. For implementation, refer to existing or laterdeveloped approaches.

In the PDN connection establishment procedure, an uplink/downlink userplane data transmission path changes to: the UE↔the target basestation↔the target U-GW, that is, transmission paths indicated by adashed line L1 g and a dashed line L2 g in FIG. 11.

In this embodiment of the present disclosure, before the UE changes fromthe idle mode to the connected mode and sends user plane data, the C-GWdetermines, according to the current location information of the UE,whether the serving U-GW needs to change, triggers a PDN connectiondeactivation procedure, and adds a reactivation request indicationduring the PDN connection deactivation procedure to request the UE toimmediately initiate a PDN connection reestablishment procedure, torecreate bearer resources on the target U-GW, ensure service continuityof subsequent user plane data transmission, and ensure user serviceexperience.

FIG. 12 is a schematic structural diagram of a control plane gateway1200 according to an embodiment of the present disclosure. As shown inFIG. 12, the control plane gateway 1200 may include a receiving unit1201, a selection unit 1202, and a tunnel establishment unit 1203.

The receiving unit 1201 is configured to receive current locationinformation of UE sent by a mobility management network element.

The selection unit 1202 is configured to select at least one forwardingU-GW for the UE according to the current location information of the UE.

In this embodiment of the present disclosure, a current location area ofthe UE falls beyond a service range of a current serving U-GW of the UE,and the C-GW needs to select an appropriate forwarding U-GW for the UEaccording to the current location area of the UE.

The tunnel establishment unit 1203 is configured to establish, for theUE, a data forwarding tunnel between a source U-GW serving the UE andthe forwarding U-GW, and a data forwarding tunnel between the forwardingU-GW and a target base station of the UE. The data forwarding tunnelsare used to transmit uplink user plane data and/or downlink user planedata of the UE in a moving process of the UE.

For an applicable scenario of this embodiment of the present disclosure,refer to the application scenarios in the embodiment shown in FIG. 2.

In the application scenario (1), after receiving a user plane dataswitchover request sent by the source base station, the mobilitymanagement network element may send a service switchover notification tothe serving C-GW of the UE. It should be understood that the mobilitymanagement network element may be an MME or another network element thathas a mobility management function of an MME. In some implementations,the mobility management network element may send the service switchovernotification by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the service switchover notification by using a newlycreated message. A specific message used for sending the serviceswitchover notification is not limited in the present disclosure.

In the application scenario (2), after receiving a location updaterequest sent by the UE, or successfully creating a radio access bearercontext for the UE, the mobility management network element may send arequest message to the serving C-GW of the UE. It should be understoodthat the mobility management network element may be an MME or anothernetwork element that has a mobility management function of an MME. Insome implementations, the mobility management network element may sendthe request message by using an existing message such as a createsession request message, a modify bearer request message, or a modifyaccess bearer request message. Alternatively, the mobility managementnetwork element may send the request message by using a newly createdmessage. A specific message used for sending the request message is notlimited in the present disclosure.

In the application scenario (3), after receiving a service request sentby the UE, or successfully creating a radio access bearer context forthe UE, the mobility management network element may send a requestmessage to the serving C-GW of the UE. It should be understood that themobility management network element may be an MME or another networkelement that has a mobility management function of an MME. In someimplementations, the mobility management network element may send therequest message by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the request message by using a newly created message. Aspecific message used for sending the request message is not limited inthe present disclosure.

The current location information of the UE includes tracking areainformation (TAI) corresponding to the current location area of the UE,serving base station information corresponding to the current locationarea of the UE, and/or the like. The corresponding TAI used when the UEis moved to the current location area is a target TAI of the UE. Thecorresponding serving base station information used when the UE is movedto the current location area is target base station information of theUE. The target base station information may be a target base station ID,a target CI, or the like. It may be understood that the current locationarea of the UE is also referred to as a target location area of the UE,that is, a location area of the UE after the UE is moved out of theservice range of the source serving base station. Similarly, the currentlocation information of the UE is also referred to as target locationinformation of the UE.

It should be understood that the moving process of the UE includesprocedures occurring in the foregoing three application scenarios,including the service switchover procedure in the application scenario(1), the location update procedure in the application scenario (2), andthe service request procedure in the application scenario (3).

It should be understood that the target base station of the UE is a basestation that provides an access service for the UE after the UE is movedto the current location area.

It should be understood that the data forwarding tunnels are implementedby creating a user plane bearer context between the source U-GW servingthe UE and the forwarding U-GW, and a user plane bearer context betweenthe forwarding U-GW and the target base station of the UE. The userplane bearer contexts include routing information required forforwarding user plane data. In some embodiments, a user plane bearercontext created on the source U-GW includes routing information of theforwarding U-GW and routing information of the source base stationserving the UE, a user plane bearer context created on the forwardingU-GW includes routing information of the source U-GW and routinginformation of the target base station, and a user plane bearer contextcreated on the target base station includes the routing information ofthe forwarding U-GW. Further, the routing information may include anaddress (typically, an IP address) and tunnel endpoint information(typically, if a GTP is used, the tunnel endpoint information is a GTPTEID).

It should be understood that the forwarding U-GW is the at least oneforwarding U-GW selected by the selection unit 1202. That the tunnelestablishment unit 1203 establishes, for the UE, a data forwardingtunnel between a source U-GW serving the UE and the forwarding U-GW, anda data forwarding tunnel between the forwarding U-GW and a target basestation of the UE is that the tunnel establishment unit 1203 establishesa communication path between the source U-GW, the at least oneforwarding U-GW, and the target base station, in order to establish adata forwarding tunnel between the two network elements from the sourceC-GW to the target base station.

In this embodiment of the present disclosure, the control plane gateway1200 determines the appropriate forwarding U-GW for the UE according tothe current location information after the movement, and establishes thedata forwarding tunnel between the forwarding U-GW and the source U-GW,and the data forwarding tunnel between the forwarding U-GW and thetarget base station of the UE, in order to ensure service continuity ina moving process of the UE, and improve user service experience.

In addition, as shown in FIG. 13, the control plane gateway may furtherinclude a sending unit 1204.

Optionally, in an embodiment, the at least one forwarding U-GW is afirst U-GW, the control plane gateway is a serving control plane gatewayused after the UE is moved to the current location area, and the controlplane gateway is the same as a serving control plane gateway used beforethe UE is moved to the current location area, and the mobilitymanagement network element is a serving mobility management networkelement used after the UE is moved to the current location area.

The receiving unit 1201 is further configured to receive a first requestsent by the mobility management network element. The first requestcarries the routing information of the target base station of the UE.

The tunnel establishment unit 1203 is configured to send a secondrequest to the first U-GW by using the sending unit 1204, and send athird request to the source U-GW by using the sending unit 1204. Thesecond request is used to request the first U-GW to establish the dataforwarding tunnel between the first U-GW and the target base station,and the data forwarding tunnel between the first U-GW and the sourceU-GW. The second request carries the routing information of the targetbase station and the routing information of the source U-GW. The thirdrequest is used to request the source U-GW to establish the dataforwarding tunnel between the source U-GW and the first U-GW, and thethird request carries the routing information of the first U-GW.

It should be understood that in this embodiment, the control planegateway 1200 is the same as the serving C-GW used before the UE is movedto the current location area, that is, the serving C-GW does not changein a moving process of the UE. It should be understood that thisembodiment is applicable to a scenario in which the serving mobilitymanagement network element changes in the moving process of the UE or ascenario in which the serving mobility management network element doesnot change in the moving process of the UE, that is, the mobilitymanagement network element may be the same as or different from aserving mobility management network element used before the UE is movedto the current location area.

Certainly, it should be understood that the control plane gateway 1200further receives a second response sent by the first U-GW according tothe second request, and a third response sent by the source U-GWaccording to the third request. The second response is used toacknowledge that the first U-GW allows establishment of the dataforwarding tunnel between the first U-GW and the target base station,and the data forwarding tunnel between the first U-GW and the sourceU-GW. Optionally, the second response may carry the routing informationof the first U-GW, such as an IP address and TEID information, and thethird response is used to acknowledge that the source U-GW allowsestablishment of the data forwarding tunnel between the source U-GW andthe first U-GW. After receiving the second response and the thirdresponse, the control plane gateway 1200 may send a first response ofthe first request to the mobility management network element.

It should be noted that the first request, the second request, or thethird request in this embodiment may be sent by using an existingmessage such as a create indirect data forwarding tunnel request, or anewly defined message. This is not limited in the present disclosure.Further, the first response, the second response, or the third responsein this embodiment may be sent by using an existing message such as acreate indirect data forwarding tunnel response, or a newly definedmessage. This is not limited in the present disclosure.

Optionally, in another embodiment, the at least one forwarding U-GWincludes a first U-GW and a second U-GW, the control plane gateway is aserving control plane gateway used after the UE is moved to the currentlocation area, the control plane gateway is the same as a servingcontrol plane gateway used before the UE is moved to the currentlocation area, the mobility management network element is a servingmobility management network element used after the UE is moved to thecurrent location area, and the mobility management network element isthe same as or different from a serving mobility management networkelement used before the UE is moved to the current location area.

The receiving unit 1201 is further configured to receive a first requestsent by the mobility management network element. The first requestcarries the routing information of the target base station of the UE.

The tunnel establishment unit 1203 is configured to send a secondrequest to the second U-GW by using the sending unit 1204, send a thirdrequest to the third U-GW by using the sending unit 1204, and send afourth request to the source U-GW by using the sending unit 1204. Thesecond request is used to request the second U-GW to establish a dataforwarding tunnel between the second U-GW and the target base station,and a data forwarding tunnel between the second U-GW and the third U-GW,the second request carries the routing information of the target basestation and routing information of the third U-GW, the third request isused to request the third U-GW to establish the data forwarding tunnelbetween the third U-GW and the second U-GW, and a data forwarding tunnelbetween the third U-GW and the source U-GW, the third request carriesrouting information of the second U-GW and the routing information ofthe source U-GW, the fourth request is used to request the source U-GWto establish the data forwarding tunnel between the source U-GW and thethird U-GW, and the fourth request carries the routing information ofthe third U-GW.

It should be understood that in this embodiment, the C-GW is the same asthe serving C-GW used before the UE is moved to the current locationarea, that is, the serving C-GW does not change in the moving process ofthe UE. It should be understood that this embodiment is applicable to ascenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Similarly, the control plane gateway 1200 further receives a secondresponse sent by the second U-GW according to the second request, athird response sent by the third U-GW according to the third request,and a fourth response sent by the source U-GW according to the fourthrequest. The second response is used to acknowledge that the second U-GWallows establishment of the data forwarding tunnel between the secondU-GW and the target base station, and the data forwarding tunnel betweenthe second U-GW and the third U-GW. Optionally, the second response maycarry the routing information of the second U-GW, such as an IP addressand TEID information. The third response is used to acknowledge that thethird U-GW allows establishment of the data forwarding tunnel betweenthe third U-GW and the second U-GW, and the data forwarding tunnelbetween the third U-GW and the source U-GW. Optionally, the thirdresponse may carry the routing information of the third U-GW, such as anIP address and TEID information. The fourth response is used toacknowledge that the source U-GW allows establishment of the dataforwarding tunnel between the source U-GW and the third U-GW. Afterreceiving the second response, the third response, and the fourthresponse, the control plane gateway 1200 may send a first response ofthe first request to the mobility management network element.

It should be noted that the first request, the second request, the thirdrequest, or the fourth request in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelrequest, or a newly defined message. This is not limited in the presentdisclosure. Further, the first response, the second response, the thirdresponse, or the fourth response in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelresponse, or a newly defined message. This is not limited in the presentdisclosure.

Optionally, in still another embodiment, the at least one forwardingU-GW is a first U-GW, the control plane gateway is a serving controlplane gateway used after the UE is moved to the current location area,the control plane gateway is different from a serving control planegateway used before the UE is moved to the current location area, themobility management network element is a serving mobility managementnetwork element used after the UE is moved to the current location area,and the mobility management network element is the same as or differentfrom a serving mobility management network element used before the UE ismoved to the current location area.

The receiving unit 1201 is further configured to receive the routinginformation of the source U-GW of the UE.

The receiving unit 1201 is further configured to receive a first requestsent by the mobility management network element. The first requestcarries the routing information of the target base station of the UE.

The tunnel establishment unit 1203 is configured to send a secondrequest to the first U-GW by using the sending unit 1204. The secondrequest is used to request the first U-GW to establish the dataforwarding tunnel between the first U-GW and the target base station,and the data forwarding tunnel between the first U-GW and the sourceU-GW, and the second request carries the routing information of thetarget base station and the routing information of the source U-GW.

It should be understood that in this embodiment, the C-GW is differentfrom the serving C-GW used before the UE is moved to the currentlocation area, that is, the serving C-GW changes in the moving processof the UE. It should be understood that this embodiment is applicable toa scenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Similarly, the control plane gateway 1200 further receives a secondresponse sent by the first U-GW according to the second request, and athird response sent by the source U-GW according to the third request.The second response is used to acknowledge that the first U-GW allowsestablishment of the data forwarding tunnel between the first U-GW andthe target base station, and the data forwarding tunnel between thefirst U-GW and the source U-GW. Optionally, the second response maycarry the routing information of the first U-GW, such as an IP addressand TEID information, and the third response is used to acknowledge thatthe source U-GW allows establishment of the data forwarding tunnelbetween the source U-GW and the first U-GW. After receiving the secondresponse and the third response, the control plane gateway 1200 may senda first response of the first request to the mobility management networkelement.

Certainly, it should be understood that, because the serving C-GW of theUE in this embodiment changes in the moving process of the UE, the C-GWis a target C-GW, that is, a serving C-GW used after the UE is moved tothe current location area. Further, the target C-GW should furtherindicate to a source C-GW via the mobility management network element,to send a data forwarding tunnel establishment request to the sourceU-GW; and send the routing information of the first U-GW to the sourceU-GW. The source C-GW is a serving C-GW used before the UE is moved tothe current location area, and the source U-GW is a serving U-GW usedbefore the UE is moved to the current location area.

It should be noted that the first request or the second request in thisembodiment may be sent by using an existing message such as a createindirect data forwarding tunnel request, or a newly defined message.This is not limited in the present disclosure. Further, the firstresponse or the second response in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelresponse, or a newly defined message. This is not limited in the presentdisclosure.

Optionally, in still another embodiment, the at least one forwardingU-GW includes a first U-GW and a second U-GW, the control plane gatewayis a serving control plane gateway used after the UE is moved to thecurrent location area, the control plane gateway is different from aserving control plane gateway used before the UE is moved to the currentlocation area, the mobility management network element is a servingmobility management network element used after the UE is moved to thecurrent location area, and the mobility management network element isthe same as or different from a serving mobility management networkelement used before the UE is moved to the current location area.

The receiving unit 1201 is further configured to receive the routinginformation of the source U-GW of the UE.

The receiving unit 1201 is further configured to receive a first requestsent by the mobility management network element. The first requestcarries the routing information of the target base station of the UE.

The tunnel establishment unit 1203 is configured to send a secondrequest to the second U-GW by using the sending unit 1204, and send athird request to the third U-GW by using the sending unit 1204. Thesecond request is used to request the second U-GW to establish a dataforwarding tunnel between the second U-GW and the target base station,and a data forwarding tunnel between the second U-GW and the third U-GW.The second request carries the routing information of the target basestation and routing information of the third U-GW. The third request isused to request the third U-GW to establish the data forwarding tunnelbetween the third U-GW and the second U-GW, and a data forwarding tunnelbetween the third U-GW and the source U-GW. The third request carriesrouting information of the second U-GW and the routing information ofthe source U-GW.

It should be understood that in this embodiment, the C-GW is differentfrom the serving C-GW used before the UE is moved to the currentlocation area, that is, the serving C-GW changes in the moving processof the UE. It should be understood that this embodiment is applicable toa scenario in which the serving mobility management network elementchanges in the moving process of the UE or a scenario in which theserving mobility management network element does not change in themoving process of the UE, that is, the mobility management networkelement may be the same as or different from a serving mobilitymanagement network element used before the UE is moved to the currentlocation area.

Similarly, the control plane gateway 1200 further receives a secondresponse sent by the second U-GW according to the second request, athird response sent by the third U-GW according to the third request,and a fourth response sent by the source U-GW according to the fourthrequest. The second response is used to acknowledge that the second U-GWallows establishment of the data forwarding tunnel between the secondU-GW and the target base station, and the data forwarding tunnel betweenthe second U-GW and the third U-GW. Optionally, the second response maycarry the routing information of the second U-GW, such as an IP addressand TEID information. The third response is used to acknowledge that thethird U-GW allows establishment of the data forwarding tunnel betweenthe third U-GW and the second U-GW, and the data forwarding tunnelbetween the third U-GW and the source U-GW. Optionally, the thirdresponse may carry the routing information of the third U-GW, such as anIP address and TEID information. The fourth response is used toacknowledge that the source U-GW allows establishment of the dataforwarding tunnel between the source U-GW and the third U-GW. Afterreceiving the second response, the third response, and the fourthresponse, the control plane gateway 1200 may send a first response ofthe first request to the mobility management network element.

Certainly, it should be understood that, because the serving C-GW of theUE in this embodiment changes in the moving process of the UE, the C-GWin this embodiment is a target C-GW, that is, a serving C-GW used afterthe UE is moved to the current location area. Further, the target C-GWshould further indicate to a source C-GW via the mobility managementnetwork element, to send a data forwarding tunnel establishment requestto the source U-GW; and send the routing information of the third U-GWto the source U-GW. The source C-GW is a serving C-GW used before the UEis moved to the current location area, and the source U-GW is a servingU-GW used before the UE is moved to the current location area.

It should be noted that the first request, the second request, or thethird request in this embodiment may be sent by using an existingmessage such as a create indirect data forwarding tunnel request, or anewly defined message. This is not limited in the present disclosure.Further, the first response, the second response, or the third responsein this embodiment may be sent by using an existing message such as acreate indirect data forwarding tunnel response, or a newly definedmessage. This is not limited in the present disclosure. Optionally, inthe foregoing four embodiments shown in FIG. 13, when the at least oneforwarding U-GW is the first U-GW, the tunnel establishment unit 1203 isfurther configured to send routing information of a target U-GW to thetarget base station via the mobility management network element.

Optionally, in the foregoing four embodiments shown in FIG. 13, when theat least one forwarding U-GW is the first U-GW, the tunnel establishmentunit 1203 is further configured to send the routing information of thefirst U-GW to the target base station via the mobility managementnetwork element.

Optionally, in the foregoing four embodiments shown in FIG. 13, when theat least one forwarding U-GW is the second U-GW and the third U-GW, thetunnel establishment unit 1203 is further configured to send the routinginformation of the second U-GW to the target base station via themobility management network element.

Optionally, in the foregoing four embodiments shown in FIG. 13, thetunnel establishment unit 1203 is further configured to send a createsession request to the target U-GW. The create session request is usedto create, on the target U-GW for the UE, a bearer context for userplane data transmission. Each created bearer context includes routinginformation of the target U-GW, and the target U-GW is a serving U-GWcorresponding to the current location area of the UE. It may beunderstood that the target U-GW is generally a serving U-GW thatprovides an optimal data transmission path for the UE in the currentlocation area. Further, the tunnel establishment unit 1203 is furtherconfigured to send the routing information of the target U-GW to thetarget base station via the mobility management network element.

Optionally, in the foregoing four embodiments shown in FIG. 13, when theat least one forwarding U-GW is the first U-GW, the first U-GW isfurther a serving U-GW selected by the control plane gateway for the UEaccording to the current location information of the UE. That is, thefirst U-GW is a target U-GW. In this case, the target D-GW can directlycommunicate with the source D-GW, that is, the target U-GW also plays arole of the forwarding U-GW. It may be understood that, when the targetU-GW cannot directly communicate with the source D-GW, the forwardingU-GW selected by the C-GW is different from the target U-GW.

The control plane gateway 1200 may further perform the method shown inFIG. 2, and implements the functions of the C-GW in the embodimentsshown in FIG. 2 to FIG. 4, FIG. 7, and FIG. 8, and functions of thetarget C-GW in the embodiment shown in FIG. 5 or FIG. 6A and FIG. 6B.Details are not described in this embodiment of the present disclosureagain.

FIG. 14 is a schematic structural diagram of a mobility managementnetwork element 1400 according to an embodiment of the presentdisclosure. The mobility management network element 1400 may include areceiving unit 1401, a selection unit 1402, and a sending unit 1403.

The receiving unit 1401 is configured to receive a forwarding relocationrequest sent by a source mobility management network element serving UE.

The forwarding relocation request carries current location informationof the UE.

The selection unit 1402 is configured to select a target C-GW of the UEaccording to the current location information of the UE.

The sending unit 1403 is configured to send the current locationinformation of the UE to the target C-GW, such that the target controlplane gateway determines a forwarding U-GW of the UE according to thecurrent location information of the UE.

The sending unit 1403 is further configured to send a data forwardingtunnel establishment request to the target control plane gateway.

The data forwarding tunnel establishment request is used to request thetarget C-GW to establish, for the UE, a data forwarding tunnel betweenthe forwarding U-GW and a source U-GW serving the UE, and a dataforwarding tunnel between the forwarding U-GW and a target base stationserving the UE.

In this embodiment of the present disclosure, after the UE is moved outof a service range of the source mobility management network element,the mobility management network element 1400 determines the target C-GWof the UE according to the current location information of the UE, andfurther establishes a data forwarding tunnel between the source U-GW andthe target base station of the UE for the UE by using the target C-GW,in order to ensure service continuity in the moving process of the UE,and improve user service experience.

Optionally, the target control plane gateway is different from a servingcontrol plane gateway used before the UE is moved to the currentlocation area (that is, the serving C-GW changes in the moving processof the UE). The sending unit 1403 is further configured to send a changenotification message to the source mobility management network element.The change notification message is used to indicate that a servingcontrol plane gateway of the UE changes to the target control planegateway.

Further, the receiving unit 1401 is further configured to receive anacknowledgment message sent by the source mobility management networkelement according to the change notification message. The acknowledgmentmessage carries routing information of the source U-GW of the UE.

The mobility management network element 1400 may further perform themethod in FIG. 9 and implement functions of the target MME in theembodiment shown in FIG. 5 or FIG. 6A and FIG. 6B. Details are notdescribed in this embodiment of the present disclosure again.

FIG. 15 is a schematic structural diagram of a control plane gateway1500 according to an embodiment of the present disclosure. The controlplane gateway 1500 includes a receiving unit 1501 configured to receivecurrent location information of the UE sent by a mobility managementnetwork element, a selection unit 1502 configured to select a targetU-GW for the UE according to the current location information of the UE,and a sending unit 1503 configured to send a request message to themobility management network element.

The request message is used to request the mobility management networkelement to release a first bearer context and indicate to the UE to senda setup request for a second bearer context. The first bearer context isa bearer context of the UE that is established on a source U-GW of theUE, and the second bearer context is a bearer context that isreestablished by the UE on the target U-GW according to the first bearercontext.

It should be understood that in this embodiment of the presentdisclosure, the location update notification message is used to notifythe C-GW that the current location area of the UE changes. For thelocation update notification, an existing message may be reused, such asa create session request message, a modify bearer request message, or amodify access bearer request message. Alternatively, a new message maybe defined. This is not limited in the present disclosure.

In this embodiment of the present disclosure, before the UE changes froman idle mode to a connected mode and sends user plane data, the controlplane gateway 1500 determines, according to the current locationinformation of the UE, whether the serving U-GW needs to change,triggers a bearer context deactivation procedure, and adds areactivation request indication during the bearer context deactivationprocedure to request the UE to immediately initiate a bearer contextreestablishment procedure, to recreate bearer resources on the targetU-GW, ensure service continuity of subsequent user plane datatransmission, and ensure user service experience.

Optionally, in an embodiment, the request message is a delete bearerrequest message, the delete bearer request message carries areactivation request indication, and the reactivation request indicationis used to indicate, by using the mobility management network element,to the UE to initiate the setup request for the second bearer contextafter the first bearer context is deleted.

It should be understood that both the MME and the UE record the firstbearer context created by the UE on the source U-GW. After receiving thedelete bearer request message, the MME deletes the first bearer contexton the MME, and indicates to the UE to delete the first bearer contexton the UE. When the delete bearer request message carries thereactivation request indication, the MME further sends the reactivationrequest indication to the UE, to indicate to the UE to resend a setuprequest for a bearer context according to content of the first bearercontext after the first bearer context is deleted, and request to createthe second bearer context. The second bearer context is a bearer contextcreated on the target U-GW based on the first bearer context.

The control plane gateway 1500 may further perform the method in FIG. 10and implement functions of the C-GW in the embodiment shown in FIG. 11.Details are not described in this embodiment of the present disclosureagain.

FIG. 16 is a schematic structural diagram of a control plane gateway1600 according to an embodiment of the present disclosure. The controlplane gateway 1600 may include a processor 1602, a memory 1603, atransmitter 1601, and a receiver 1604.

The receiver 1604, the transmitter 1601, the processor 1602, and thememory 1603 are connected to each other by using a bus 1606. The bus1606 may be an ISA bus, a PCI bus, an EISA bus, or the like. The bus maybe classified into an address bus, a data bus, a control bus, and thelike. For ease of representation, in FIG. 16, the bus 1606 is indicatedby using only one double-headed arrow. However, it does not indicatethat there is only one bus or only one type of bus. In someimplementations, the transmitter 1601 and the receiver 1604 may becoupled to an antenna 1605.

The memory 1603 is configured to store a program. For example, theprogram may include program code, and the program code includes acomputer operation instruction. The memory 1603 may include a read-onlymemory and a random access memory, and provides an instruction and datafor the processor 1602. The memory 1603 may include a high-speed RAMmemory, and may further include a nonvolatile memory, for example, atleast one magnetic disk memory.

The processor 1602 executes the program stored in the memory 1603 and isconfigured to perform the following operations: receiving, by using thereceiver 1604, current location information of UE sent by a mobilitymanagement network element; selecting at least one forwarding U-GW forthe UE according to the current location information of the UE; andestablishing, by using the transmitter 1601 for the UE, a dataforwarding tunnel between a source U-GW serving the UE and theforwarding U-GW, and a data forwarding tunnel between the forwardingU-GW and a target base station of the UE, where the data forwardingtunnels are used to transmit uplink user plane data and/or downlink userplane data of the UE in a moving process of the UE.

For an applicable scenario in this embodiment of the present disclosure,refer to the application scenarios in the embodiment shown in FIG. 2.

In the application scenario (1), after receiving a user plane dataswitchover request sent by the source base station, the mobilitymanagement network element may send a service switchover notification tothe serving C-GW of the UE. It should be understood that the mobilitymanagement network element may be an MME or another network element thathas a mobility management function of an MME. In some implementations,the mobility management network element may send the service switchovernotification by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the service switchover notification by using a newlycreated message. A specific message used for sending the serviceswitchover notification is not limited in the present disclosure.

In the application scenario (2), after receiving a location updaterequest sent by the UE, or successfully creating a radio access bearercontext for the UE, the mobility management network element may send arequest message to the serving C-GW of the UE. It should be understoodthat the mobility management network element may be an MME or anothernetwork element that has a mobility management function of an MME. Insome implementations, the mobility management network element may sendthe request message by using an existing message such as a createsession request message, a modify bearer request message, or a modifyaccess bearer request message. Alternatively, the mobility managementnetwork element may send the request message by using a newly createdmessage. A specific message used for sending the request message is notlimited in the present disclosure.

In the application scenario (3), after receiving a service request sentby the UE, or successfully creating a radio access bearer context forthe UE, the mobility management network element may send a requestmessage to the serving C-GW of the UE. It should be understood that themobility management network element may be an MME or another networkelement that has a mobility management function of an MME. In someimplementations, the mobility management network element may send therequest message by using an existing message such as a create sessionrequest message, a modify bearer request message, or a modify accessbearer request message. Alternatively, the mobility management networkelement may send the request message by using a newly created message. Aspecific message used for sending the request message is not limited inthe present disclosure.

The current location information of the UE includes tracking areainformation (TAI) corresponding to the current location area of the UE,serving base station information corresponding to the current locationarea of the UE, and/or the like. The corresponding TAI used when the UEis moved to the current location area is a target TAI of the UE. Thecorresponding serving base station information used after the UE ismoved to the current location area is target base station information ofthe UE. The target base station information may be a target base stationID, a target CI, or the like. It may be understood that the currentlocation area of the UE is also referred to as a target location area ofthe UE, that is, a location area of the UE after the UE is moved out ofthe service range of the source serving base station. Similarly, thecurrent location information of the UE is also referred to as targetlocation information of the UE.

It should be understood that the moving process of the UE includesprocedures occurring in the foregoing three application scenarios,including the service switchover procedure in the application scenario(1), the location update procedure in the application scenario (2), andthe service request procedure in the application scenario (3).

It should be understood that the target base station of the UE is a basestation that provides an access service for the UE after the UE is movedto the current location area.

It should be understood that the data forwarding tunnels are implementedby creating a user plane bearer context between the source U-GW servingthe UE and the forwarding U-GW, and a user plane bearer context betweenthe forwarding U-GW and the target base station of the UE. The userplane bearer contexts include routing information required forforwarding user plane data, including routing information of the sourceU-GW, routing information of the forwarding U-GW, and routinginformation of the target base station. For example, the routinginformation may include an address (typically an IP address) and tunnelendpoint information (typically, if a GTP is used, the tunnel endpointinformation is a GTP TEID).

It should be understood that the forwarding U-GW is the at least oneforwarding U-GW selected by the processor 1602. That the processor 1602establishes, for the UE, a data forwarding tunnel between the sourceU-GW serving the UE and the forwarding U-GW, and a data forwardingtunnel between the forwarding U-GW and the target base station of the UEis that the process 1602 establishes a communication path between thesource U-GW, the at least one forwarding U-GW, and the target basestation, in order to establish a data forwarding tunnel between the twonetwork elements from the source C-GW to the target base station.

The foregoing method that is performed by the C-GW disclosed in anyembodiment in FIG. 2 to FIG. 4 of the present disclosure or that isperformed by the target C-GW disclosed in any embodiment in FIG. 5, FIG.6A, and FIG. 6B may be applied to the processor 1602, or may beimplemented by the processor 1602. The processor 1602 may be anintegrated circuit chip and has a signal processing capability. In animplementation process, the steps in the foregoing method may becompleted by means of an integrated logic circuit of hardware in theprocessor 1602 or an instruction in a form of software. The processor1602 may be a general purpose processor, including a central processingunit (CPU), a network processor (NP), and the like, or may be a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a field programmable gate array (FPGA), another programmablelogical device, a discrete gate or transistor logic device, or adiscrete hardware component. The processor 1602 may implement or performthe methods, steps, and logical block diagrams disclosed in theembodiments of the present disclosure. The general purpose processor maybe a microprocessor, or the processor may be any conventional processor,or the like. The steps of the method disclosed with reference to theembodiments of the present disclosure may be directly performed andcompleted by using a hardware decoding processor, or performed andcompleted by combining hardware and software modules in a decodingprocessor. The software module may be located in a mature storage mediumin the field, such as a random access memory, a flash memory, aread-only memory, a programmable read-only memory, anelectrically-erasable programmable memory, or a register. The storagemedium is located in the memory 1603. The processor 1602 readsinformation in the memory 1603, and completes the steps of the foregoingmethod in combination with hardware of the processor 1602.

In this embodiment of the present disclosure, the control plane gateway1600 determines the appropriate forwarding U-GW for the UE according tothe current location information after the movement, and establishes thedata forwarding tunnel between the forwarding U-GW and the source U-GW,and the data forwarding tunnel between the forwarding U-GW and thetarget base station of the UE, in order to ensure service continuity inthe moving process of the UE, and improve user service experience.

Optionally, in an embodiment, the at least one forwarding U-GW is afirst U-GW, the control plane gateway is a serving control plane gatewayused after the UE is moved to the current location area, the controlplane gateway is the same as a serving control plane gateway used beforethe UE is moved to the current location area, the mobility managementnetwork element is a serving mobility management network element usedafter the UE is moved to the current location area, and the mobilitymanagement network element is the same as or different from a servingmobility management network element used before the UE is moved to thecurrent location area.

The processor 1602 is further configured to receive, by using thereceiver 1604, a first request sent by the mobility management networkelement. The first request carries the routing information of the targetbase station of the UE.

In a process of establishing, by using the transmitter 1601 for the UE,the data forwarding tunnel between the source U-GW serving the UE andthe forwarding U-GW, and/or the data forwarding tunnel between theforwarding U-GW and the target base station of the UE, the processor1602 is configured to send a second request to the first U-GW by usingthe transmitter 1601, and send a third request to the source U-GW byusing the transmitter 1601. The second request is used to request thefirst U-GW to allow establishment of the data forwarding tunnel betweenthe first U-GW and the target base station, and the data forwardingtunnel between the first U-GW and the source U-GW, the second requestcarries the routing information of the target base station and therouting information of the source U-GW. The third request is used torequest the source U-GW to establish the data forwarding tunnel betweenthe source U-GW and the first U-GW, and the third request carries therouting information of the first U-GW.

It should be understood that in this embodiment, the control planegateway 1600 is the same as the serving C-GW used before the UE is movedto the current location area, that is, the serving C-GW does not changein the moving process of the UE. It should be understood that thisembodiment is applicable to a scenario in which the serving mobilitymanagement network element changes in the moving process of the UE or ascenario in which the serving mobility management network element doesnot change in the moving process of the UE, that is, the mobilitymanagement network element may be the same as or different from aserving mobility management network element used before the UE is movedto the current location area.

Certainly, it should be understood that the control plane gateway 1600further receives a second response sent by the first U-GW according tothe second request, and a third response sent by the source U-GWaccording to the third request. The second response is used toacknowledge that the first U-GW allows establishment of the dataforwarding tunnel between the first U-GW and the target base station,and the data forwarding tunnel between the first U-GW and the sourceU-GW. Optionally, the second response may carry the routing informationof the first U-GW, such as an IP address and TEID information, and thethird response is used to acknowledge that the source U-GW allowsestablishment of the data forwarding tunnel between the source U-GW andthe first U-GW. After receiving the second response and the thirdresponse, the control plane gateway 1600 may send a first response ofthe first request to the mobility management network element.

It should be noted that the first request, the second request, or thethird request in this embodiment may be sent by using an existingmessage such as a create indirect data forwarding tunnel request, or anewly defined message. This is not limited in the present disclosure.Further, the first response, the second response, or the third responsein this embodiment may be sent by using an existing message such as acreate indirect data forwarding tunnel response, or a newly definedmessage. This is not limited in the present disclosure.

Optionally, in another embodiment, the at least one forwarding U-GWincludes a first U-GW and a second U-GW, the control plane gateway is aserving control plane gateway used after the UE is moved to the currentlocation area, the control plane gateway is the same as a servingcontrol plane gateway used before the UE is moved to the currentlocation area, the mobility management network element is a servingmobility management network element used after the UE is moved to thecurrent location area, and the mobility management network element isthe same as or different from a serving mobility management networkelement used before the UE is moved to the current location area.

The processor 1602 is further configured to receive, by using thereceiver 1604, a first request sent by the mobility management networkelement. The first request carries the routing information of the targetbase station of the UE.

In a process of establishing, by using the transmitter 1601 for the UE,the data forwarding tunnel between the source U-GW serving the UE andthe forwarding U-GW, and the data forwarding tunnel between theforwarding U-GW and the target base station of the UE, the processor1602 is configured to:

send a second request to the second U-GW by using the transmitter 1601,send a third request to the third U-GW by using the transmitter 1601,and send a fourth request to the source U-GW by using the transmitter1601, where the second request is used to request the second U-GW toestablish a data forwarding tunnel between the second U-GW and thetarget base station, and a data forwarding tunnel between the secondU-GW and the third U-GW, the second request carries the routinginformation of the target base station and routing information of thethird U-GW, the third request is used to request the third U-GW toestablish the data forwarding tunnel between the third U-GW and thesecond U-GW, and a data forwarding tunnel between the third U-GW and thesource U-GW, the third request carries routing information of the secondU-GW and the routing information of the source U-GW, the fourth requestis used to request the source U-GW to establish the data forwardingtunnel between the source U-GW and the third U-GW, and the fourthrequest carries the routing information of the third U-GW.

It should be understood that in this embodiment, the control planegateway 1600 is the same as the serving C-GW used before the UE is movedto the current location area, that is, the serving C-GW does not changein the moving process of the UE. It should be understood that thisembodiment is applicable to a scenario in which the serving mobilitymanagement network element changes in the moving process of the UE or ascenario in which the serving mobility management network element doesnot change in the moving process of the UE, that is, the mobilitymanagement network element may be the same as or different from aserving mobility management network element used before the UE is movedto the current location area.

Similarly, the control plane gateway 1600 further receives a secondresponse sent by the second U-GW according to the second request, athird response sent by the third U-GW according to the third request,and a fourth response sent by the source U-GW according to the fourthrequest. The second response is used to acknowledge that the second U-GWallows establishment of the data forwarding tunnel between the secondU-GW and the target base station, and the data forwarding tunnel betweenthe second U-GW and the third U-GW. Optionally, the second response maycarry the routing information of the second U-GW, such as an IP addressand TEID information. The third response is used to acknowledge that thethird U-GW allows establishment of the data forwarding tunnel betweenthe third U-GW and the second U-GW, and the data forwarding tunnelbetween the third U-GW and the source U-GW. Optionally, the thirdresponse may carry the routing information of the third U-GW, such as anIP address and TEID information. The fourth response is used toacknowledge that the source U-GW allows establishment of the dataforwarding tunnel between the source U-GW and the third U-GW. Afterreceiving the second response, the third response, and the fourthresponse, the control plane gateway 1600 may send a first response ofthe first request to the mobility management network element.

It should be noted that the first request, the second request, the thirdrequest, or the fourth request in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelrequest, or a newly defined message. This is not limited in the presentdisclosure. Further, the first response, the second response, the thirdresponse, or the fourth response in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelresponse, or a newly defined message. This is not limited in the presentdisclosure.

Optionally, in still another embodiment, the at least one forwardingU-GW is a first U-GW, the control plane gateway is a serving controlplane gateway used after the UE is moved to the current location area,the control plane gateway is different from a serving control planegateway used before the UE is moved to the current location area, themobility management network element is a serving mobility managementnetwork element used after the UE is moved to the current location area,and the mobility management network element is the same as or differentfrom a serving mobility management network element used before the UE ismoved to the current location area.

The processor 1602 is further configured to receive, by using thereceiver 1604, the routing information of the source U-GW of the UE.

The processor 1602 is further configured to receive, by using thereceiver 1604, a first request sent by the mobility management networkelement. The first request carries the routing information of the targetbase station of the UE.

In a process of establishing, by using the transmitter 1601 for the UE,the data forwarding tunnel between the source U-GW serving the UE andthe forwarding U-GW, and the data forwarding tunnel between theforwarding U-GW and the target base station of the UE, the processor1602 is configured to send a second request to the first U-GW by usingthe transmitter 1601, where the second request is used to request thefirst U-GW to establish the data forwarding tunnel between the firstU-GW and the target base station, and the data forwarding tunnel betweenthe first U-GW and the source U-GW, and the second request carries therouting information of the target base station and the routinginformation of the source U-GW.

It should be understood that in this embodiment, the control planegateway 1600 is different from the serving C-GW used before the UE ismoved to the current location area, that is, the serving C-GW changes inthe moving process of the UE. It should be understood that thisembodiment is applicable to a scenario in which the serving mobilitymanagement network element changes in the moving process of the UE or ascenario in which the serving mobility management network element doesnot change in the moving process of the UE, that is, the mobilitymanagement network element may be the same as or different from aserving mobility management network element used before the UE is movedto the current location area.

Similarly, the control plane gateway 1600 further receives a secondresponse sent by the first U-GW according to the second request, and athird response sent by the source U-GW according to the third request.The second response is used to acknowledge that the first U-GW allowsestablishment of the data forwarding tunnel between the first U-GW andthe target base station, and the data forwarding tunnel between thefirst U-GW and the source U-GW. Optionally, the second response maycarry the routing information of the first U-GW, such as an IP addressand TEID information, and the third response is used to acknowledge thatthe source U-GW allows establishment of the data forwarding tunnelbetween the source U-GW and the first U-GW. After receiving the secondresponse and the third response, the control plane gateway 1600 may senda first response of the first request to the mobility management networkelement.

Certainly, it should be understood that, because the serving C-GW of theUE in this embodiment changes in the moving process of the UE, thecontrol plane gateway 1600 is a target C-GW, that is, a serving C-GWused after the UE is moved to the current location area. Further, theprocessor 1602 should further indicate to a source C-GW via the mobilitymanagement network element, to send a data forwarding tunnelestablishment request to the source U-GW; and send the routinginformation of the first U-GW to the source U-GW. The source C-GW is aserving C-GW used before the UE is moved to the current location area,and the source U-GW is a serving U-GW used before the UE is moved to thecurrent location area.

It should be noted that the first request or the second request in thisembodiment may be sent by using an existing message such as a createindirect data forwarding tunnel request, or a newly defined message.This is not limited in the present disclosure. Further, the firstresponse or the second response in this embodiment may be sent by usingan existing message such as a create indirect data forwarding tunnelresponse, or a newly defined message. This is not limited in the presentdisclosure.

Optionally, in still another embodiment, the at least one forwardingU-GW includes a first U-GW and a second U-GW, the control plane gatewayis a serving control plane gateway used after the UE is moved to thecurrent location area, the control plane gateway is different from aserving control plane gateway used before the UE is moved to the currentlocation area, the mobility management network element is a servingmobility management network element used after the UE is moved to thecurrent location area, and the mobility management network element isthe same as or different from a serving mobility management networkelement used before the UE is moved to the current location area.

The processor 1602 is further configured to receive, by using thereceiver 1604, the routing information of the source U-GW of the UE.

The processor 1602 is further configured to receive, by using thereceiver 1604, a first request sent by the mobility management networkelement. The first request carries the routing information of the targetbase station of the UE.

In a process of establishing, by using the transmitter 1601 for the UE,the data forwarding tunnel between the source U-GW serving the UE andthe forwarding U-GW, and the data forwarding tunnel between theforwarding U-GW and the target base station of the UE, the processor1602 is configured to:

send a second request to the second U-GW by using the transmitter 1601,and send a third request to the third U-GW by using the transmitter1601, where the second request is used to request the second U-GW toestablish a data forwarding tunnel between the second U-GW and thetarget base station, and a data forwarding tunnel between the secondU-GW and the third U-GW, the second request carries the routinginformation of the target base station and routing information of thethird U-GW, the third request is used to request the third U-GW toestablish the data forwarding tunnel between the third U-GW and thesecond U-GW, and a data forwarding tunnel between the third U-GW and thesource U-GW, and the third request carries routing information of thesecond U-GW and the routing information of the source U-GW.

It should be understood that in this embodiment, the control planegateway 1600 is different from the serving C-GW used before the UE ismoved to the current location area, that is, the serving C-GW changes inthe moving process of the UE. It should be understood that thisembodiment is applicable to a scenario in which the serving mobilitymanagement network element changes in the moving process of the UE or ascenario in which the serving mobility management network element doesnot change in the moving process of the UE, that is, the mobilitymanagement network element may be the same as or different from aserving mobility management network element used before the UE is movedto the current location area.

Similarly, the control plane gateway 1600 further receives a secondresponse sent by the second U-GW according to the second request, athird response sent by the third U-GW according to the third request,and a fourth response sent by the source U-GW according to the fourthrequest. The second response is used to acknowledge that the second U-GWallows establishment of the data forwarding tunnel between the secondU-GW and the target base station, and the data forwarding tunnel betweenthe second U-GW and the third U-GW. Optionally, the second response maycarry the routing information of the second U-GW, such as an IP addressand TEID information. The third response is used to acknowledge that thethird U-GW allows establishment of the data forwarding tunnel betweenthe third U-GW and the second U-GW, and the data forwarding tunnelbetween the third U-GW and the source U-GW. Optionally, the thirdresponse may carry the routing information of the third U-GW, such as anIP address and TEID information. The fourth response is used toacknowledge that the source U-GW allows establishment of the dataforwarding tunnel between the source U-GW and the third U-GW. Afterreceiving the second response, the third response, and the fourthresponse, the control plane gateway 1600 may send a first response ofthe first request to the mobility management network element.

Certainly, it should be understood that, because the serving C-GW of theUE in this embodiment changes in the moving process of the UE, thecontrol plane gateway 1600 in this embodiment is a target C-GW, that is,a serving C-GW used after the UE is moved to the current location area.Further, the processor 1602 should further indicate to a source C-GW viathe mobility management network element, to send a data forwardingtunnel establishment request to the source U-GW; and send the routinginformation of the third U-GW to the source U-GW. The source C-GW is aserving C-GW used before the UE is moved to the current location area,and the source U-GW is a serving U-GW used before the UE is moved to thecurrent location area.

It should be noted that the first request, the second request, or thethird request in this embodiment may be sent by using an existingmessage such as a create indirect data forwarding tunnel request, or anewly defined message. This is not limited in the present disclosure.Further, the first response, the second response, or the third responsein this embodiment may be sent by using an existing message such as acreate indirect data forwarding tunnel response, or a newly definedmessage. This is not limited in the present disclosure.

Optionally, in the foregoing four embodiments of FIG. 16, when the atleast one forwarding U-GW is the first U-GW, the processor 1602 isfurther configured to send, by using the transmitter 1601, routinginformation of a target U-GW to the target base station via the mobilitymanagement network element.

Optionally, in the foregoing four embodiments of FIG. 16, when the atleast one forwarding U-GW is the first U-GW, the processor 1602 isfurther configured to send the routing information of the first U-GW tothe target base station via the mobility management network element.

Optionally, in the foregoing four embodiments of FIG. 16, when the atleast one forwarding U-GW is the second U-GW and the third U-GW, theprocessor 1602 is further configured to send the routing information ofthe second U-GW to the target base station via the mobility managementnetwork element.

Optionally, in the foregoing four embodiments of FIG. 16, the processor1602 is further configured to send a create session request to thetarget U-GW by using the transmitter 1601, where the create sessionrequest is used to create, on the target U-GW for the UE, a bearercontext for user plane data transmission, each created bearer contextincludes routing information of the target U-GW, and the target U-GW isa serving U-GW corresponding to the current location area of the UE. Itmay be understood that the target U-GW is generally a serving U-GW thatprovides an optimal data transmission path for the UE in the currentlocation area. Further, the processor 1602 is further configured to sendthe routing information of the target U-GW to the target base stationvia the mobility management network element.

Optionally, in the foregoing four embodiments of FIG. 16, when the atleast one forwarding U-GW is the first U-GW, the first U-GW is further aserving U-GW selected by the control plane gateway for the UE accordingto the current location information of the UE. That is, the first U-GWis a target U-GW. In this case, the target D-GW can directly communicatewith the source D-GW, that is, the target U-GW also plays a role of theforwarding U-GW. It may be understood that, when the target U-GW cannotdirectly communicate with the source D-GW, the forwarding U-GW selectedby the C-GW is different from the target U-GW.

The control plane gateway 1600 may further perform the method shown inFIG. 2, and implements the functions of the C-GW in the embodimentsshown in FIG. 2 to FIG. 4, FIG. 7, and FIG. 8, and functions of thetarget C-GW in the embodiment shown in FIG. 5 or FIG. 6A and FIG. 6B.Details are not described in this embodiment of the present disclosureagain.

FIG. 17 is a schematic structural diagram of a mobility managementnetwork element 1700 according to an embodiment of the presentdisclosure. The mobility management network element 1700 may include aprocessor 1702, a memory 1703, a transmitter 1701, and a receiver 1704.

The receiver 1704, the transmitter 1701, the processor 1702, and thememory 1703 are connected to each other by using a bus 1706. The bus1706 may be an ISA bus, a PCI bus, an EISA bus, or the like. The bus maybe classified into an address bus, a data bus, a control bus, and thelike. For ease of representation, in FIG. 17, the bus 1706 is indicatedby using only one double-headed arrow. However, it does not indicatethat there is only one bus or only one type of bus. In someimplementations, the transmitter 1701 and the receiver 1704 may becoupled to an antenna 1705.

The memory 1703 is configured to store a program. For example, theprogram may include program code, and the program code includes acomputer operation instruction. The memory 1703 may include a read-onlymemory and a random access memory, and provides an instruction and datafor the processor 1702. The memory 1703 may include a high-speed RAMmemory, and may further include a nonvolatile memory, for example, atleast one magnetic disk memory.

The processor 1702 executes the program stored in the memory 1703 and isconfigured to perform the following operations: receiving, by using thereceiver 1704, a forwarding relocation request sent by a source mobilitymanagement network element serving UE, where the forwarding relocationrequest carries current location information of the UE; selecting atarget C-GW of the UE according to the current location information ofthe UE; sending the current location information of the UE to the C-GWby using the transmitter 1701, such that the C-GW determines aforwarding U-GW of the UE according to the current location informationof the UE; and sending a data forwarding tunnel establishment request tothe target control plane gateway by using the transmitter 1701, wherethe data forwarding tunnel establishment request is used to request thetarget C-GW to establish, for the UE, a data forwarding tunnel betweenthe forwarding U-GW and a source U-GW serving the UE, and a dataforwarding tunnel between the forwarding U-GW and a target base stationserving the UE.

The foregoing method that is performed by the mobility managementnetwork element disclosed in the embodiment shown in FIG. 9 of thepresent disclosure or that is performed by the target MME disclosed inthe embodiment shown in FIG. 5 or FIG. 6A and FIG. 6B may be applied tothe processor 1702, or may be implemented by the processor 1702. Theprocessor 1702 may be an integrated circuit chip and has a signalprocessing capability. In an implementation process, the steps in theforegoing method may be completed by means of an integrated logiccircuit of hardware in the processor 1702 or an instruction in a form ofsoftware. The processor 1702 may be a general purpose processor,including a CPU, a NP, and the like, or may be a DSP, an ASIC, a FPGA,another programmable logical device, a discrete gate or transistor logicdevice, or a discrete hardware component. The processor 1702 mayimplement or perform the methods, steps, and logical block diagramsdisclosed in the embodiments of the present disclosure. The generalpurpose processor may be a microprocessor, or the processor may be anyconventional processor, or the like. The steps of the method disclosedwith reference to the embodiments of the present disclosure may bedirectly performed and completed by using a hardware decoding processor,or performed and completed by combining hardware and software modules ina decoding processor. The software module may be located in a maturestorage medium in the field, such as a random access memory, a flashmemory, a read-only memory, a programmable read-only memory, anelectrically-erasable programmable memory, or a register. The storagemedium is located in the memory 1703. The processor 1702 readsinformation in the memory 1703, and completes the steps of the foregoingmethod in combination with hardware of the processor 1702.

In this embodiment of the present disclosure, after the UE is moved outof a service range of the source mobility management network element,the mobility management network element 1700 determines the target C-GWof the UE according to the current location information of the UE, andfurther establishes a data forwarding tunnel between the source U-GW andthe target base station of the UE for the UE by using the target C-GW,in order to ensure service continuity in a moving process of the UE, andimprove user service experience.

Optionally, the target control plane gateway is different from a servingcontrol plane gateway used before the UE is moved to the currentlocation area (that is, the serving C-GW changes in a moving process ofthe UE). The processor 1702 is further configured to send a changenotification message to the source mobility management network elementby using the transmitter 1701. The change notification message is usedto indicate that a serving control plane gateway of the UE changes tothe target control plane gateway.

Further, the processor 1702 is further configured to receive, by usingthe receiver 1704, an acknowledgment message sent by the source mobilitymanagement network element according to the change notification message.The acknowledgment message carries routing information of the sourceU-GW of the UE.

The mobility management network element 1700 may further perform themethod in FIG. 9 and implement functions of the target MME in theembodiment shown in FIG. 5 or FIG. 6A and FIG. 6B. Details are notdescribed in this embodiment of the present disclosure again.

FIG. 18 is a schematic structural diagram of a control plane gateway1800 according to an embodiment of the present disclosure. The controlplane gateway 1800 may include a processor 1802, a memory 1803, atransmitter 1801, and a receiver 1804.

The receiver 1804, the transmitter 1801, the processor 1802, and thememory 1803 are connected to each other by using a bus 1806. The bus1806 may be an ISA bus, a PCI bus, an EISA bus, or the like. The bus maybe classified into an address bus, a data bus, a control bus, and thelike. For ease of representation, in FIG. 18, the bus 1806 is indicatedby using only one double-headed arrow. However, it does not indicatethat there is only one bus or only one type of bus. In someimplementations, the transmitter 1801 and the receiver 1804 may becoupled to an antenna 1805.

The memory 1803 is configured to store a program. For example, theprogram may include program code, and the program code includes acomputer operation instruction. The memory 1803 may include a read-onlymemory and a random access memory, and provides an instruction and datafor the processor 1802. The memory 1803 may include a high-speed RAMmemory, and may further include a nonvolatile memory, for example, atleast one magnetic disk memory.

The processor 1802 executes the program stored in the memory 1803 and isconfigured to perform the following operations: receiving, by using thereceiver 1804, current location information of the UE sent by a mobilitymanagement network element; selecting a target U-GW for the UE accordingto the current location information of the UE; and sending, by using thetransmitter 1801, a request message to the mobility management networkelement, where the request message is used to request the mobilitymanagement network element to release a first bearer context andindicate to the UE to send a setup request for a second bearer context,the first bearer context is a bearer context of the UE that isestablished on a source U-GW of the UE, and the second bearer context isa bearer context that is reestablished by the UE on the target U-GWaccording to the first bearer context.

It should be understood that in this embodiment of the presentdisclosure, the location update notification message is used to notifythe C-GW that the current location area of the UE changes. For thelocation update notification, an existing message may be reused, such asa create session request message, a modify bearer request message, or amodify access bearer request message. Alternatively, a new message maybe defined. This is not limited in the present disclosure.

The foregoing method that is performed by the C-GW disclosed in anyembodiment in FIG. 10 and FIG. 11 of the present disclosure may beapplied to the processor 1802, or may be implemented by the processor1802. The processor 1802 may be an integrated circuit chip and has asignal processing capability. In an implementation process, the steps inthe foregoing method may be completed by means of an integrated logiccircuit of hardware in the processor 1802 or an instruction in a form ofsoftware. The processor 1802 may be a general purpose processor,including a CPU, a NP, and the like, or may be a DSP, an ASIC, a FPGA,another programmable logical device, a discrete gate or transistor logicdevice, or a discrete hardware component. The processor 1802 mayimplement or perform the methods, steps, and logical block diagramsdisclosed in the embodiments of the present disclosure. The generalpurpose processor may be a microprocessor, or the processor may be anyconventional processor, or the like. The steps of the method disclosedwith reference to the embodiments of the present disclosure may bedirectly performed and completed by using a hardware decoding processor,or performed and completed by combining hardware and software modules ina decoding processor. The software module may be located in a maturestorage medium in the field, such as a random access memory, a flashmemory, a read-only memory, a programmable read-only memory, anelectrically-erasable programmable memory, or a register. The storagemedium is located in the memory 1803. The processor 1802 readsinformation in the memory 1803, and completes the steps of the foregoingmethod in combination with hardware of the processor 1802.

In this embodiment of the present disclosure, before the UE changes froman idle mode to a connected mode and sends user plane data, the controlplane gateway 1800 determines, according to the current locationinformation of the UE, whether the serving U-GW needs to change,triggers a bearer context deactivation procedure, and adds areactivation request indication during the bearer context deactivationprocedure to request the UE to immediately initiate a bearer contextreestablishment procedure, to recreate bearer resources on the targetU-GW, ensure service continuity of subsequent user plane datatransmission, and ensure user service experience.

Optionally, in an embodiment, the request message is a delete bearerrequest message, the delete bearer request message carries areactivation request indication, and the reactivation request indicationis used via the mobility management network element to indicate to theUE to initiate the setup request for the second bearer context after thefirst bearer context is deleted.

It should be understood that both the MME and the UE record the firstbearer context created by the UE on the source U-GW. After receiving thedelete bearer request message, the MME deletes the first bearer contexton the MME, and indicates to the UE to delete the first bearer contexton the UE. When the delete bearer request message carries thereactivation request indication, the MME further sends the reactivationrequest indication to the UE, to indicate to the UE to resend a setuprequest for a bearer context according to content of the first bearercontext after the first bearer context is deleted, and request to createthe second bearer context. The second bearer context is a bearer contextcreated on the target U-GW based on the first bearer context.

The control plane gateway 1800 may further perform the method in FIG. 10and implement functions of the C-GW in the embodiment shown in FIG. 11.Details are not described in this embodiment of the present disclosureagain.

It should be understood that sequence numbers of the foregoing processesdo not mean execution sequences in various embodiments of the presentdisclosure. The execution sequences of the processes should bedetermined according to functions and internal logic of the processes,and should not be construed as any limitation on the implementationprocesses of the embodiments of the present disclosure.

A person of ordinary skill in the art may be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units and algorithm steps may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the present disclosure.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, reference may bemade to a corresponding process in the foregoing method embodiments, anddetails are not described herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected according toactual needs to achieve the objectives of the solutions of theembodiments.

In addition, functional units in the embodiments of the presentdisclosure may be integrated into one processing unit, or each of theunits may exist alone physically, or two or more units are integratedinto one unit.

When the functions are implemented in the form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer-readable storage medium. Based on such anunderstanding, the technical solutions of the present disclosure, or thepart contributing to other approaches, or some of the technicalsolutions may be implemented in a form of a software product. Thesoftware product is stored in a storage medium, and includes severalinstructions for instructing a computer device (which may be a personalcomputer, a server, or a network device) to perform all or some of thesteps of the methods described in the embodiments of the presentdisclosure. The foregoing storage medium may include any medium that canstore program code, such as a USB flash drive, a removable hard disk, aread-only memory (ROM), a random access memory (RAM), a magnetic disk,or an optical disc.

The foregoing descriptions are merely example implementations of thepresent disclosure, but are not intended to limit the protection scopeof the present disclosure. Any variation or replacement readily figuredout by a person skilled in the art within the technical scope disclosedin the present disclosure shall fall within the protection scope of thepresent disclosure. Therefore, the protection scope of the presentdisclosure shall be subject to the protection scope of the claims.

What is claimed is:
 1. A communication system, comprising: a mobilitymanagement network element configured to serve as a serving mobilitymanagement network element after a user equipment is moved to a locationarea associated with location information; at least one forwarding userplane gateway, wherein the at least one forwarding user plane gateway isa first user plane gateway; and a control plane gateway in communicationwith the mobility management network element and the at least oneforwarding user plane gateway, wherein the control plane gateway acts asa serving control plane gateway for the user equipment, and wherein thecontrol plane gateway is configured to: receive the location informationof the user equipment from the mobility management network element;select the at least one forwarding user plane gateway for the userequipment according to the location information of the user equipment;and establish, with the at least one forwarding user plane gateway, adata forwarding tunnel for transmitting downlink user plane data of theuser equipment by: receiving a first request from the mobilitymanagement network element, wherein the first request carries routinginformation of a target base station; sending a second request to thefirst user plane gateway, wherein the second request carries the routinginformation of the target base station; and sending a third request to asource user plane gateway, wherein the third request carries routinginformation of the first user plane gateway.
 2. The communication systemaccording to claim 1, wherein the mobility management network element isconfigured to send the location information of the user equipment to thecontrol plane gateway.
 3. The communication system according to claim 1,wherein the control plane gateway is further configured to determine,according to the location information of the user equipment, that theuser equipment has moved out of service range of the source user planegateway serving the user equipment.
 4. The communication systemaccording to claim 1, wherein the location information of the userequipment is target location information of the user equipment.
 5. Thecommunication system according to claim 1, wherein the locationinformation of the user equipment comprises at least one tracking areaidentity (TAI).
 6. The communication system according to claim 1,wherein the location information of the user equipment comprises servingbase station information.
 7. The communication system according to claim1, wherein the control plane gateway is further configured to send acreate session request to a target user plane gateway for the userequipment, wherein the create session request is to be used to create,on the target user plane gateway for the user equipment, a bearercontext for user plane data transmission, wherein each created bearercontext comprises routing information of the target user plane gateway,wherein the target user plane gateway is a serving user plane gatewaycorresponding to the location area associated with the locationinformation, and wherein the target user plane gateway is configured toreceive the create session request.
 8. The communication systemaccording to claim 7, further comprising the target base station,wherein the control plane gateway is further configured to send therouting information of the target user plane gateway to the target basestation via the mobility management network element, and wherein thetarget base station is configured to receive the routing information ofthe target user plane gateway via the mobility management networkelement.
 9. The communication system according to claim 1, furthercomprising the target base station, wherein the control plane gateway isfurther configured to send routing information of the first user planegateway to the target base station via the mobility management networkelement, and wherein the target base station is configured to receivethe routing information of the first user plane gateway via the mobilitymanagement network element.
 10. The communication system according toclaim 1, wherein the first user plane gateway is a serving user planegateway selected by the control plane gateway for the user equipmentaccording to the location information of the user equipment.
 11. Acommunication system, comprising: mobility management network elementconfigured to serve as a serving mobility management network elementafter a user equipment is moved to a location area associated withlocation information; at least one forwarding user plane gatewaycomprising a second user plane gateway and a third user plane gateway;and a control plane gateway in communication with the mobilitymanagement network element and the at least one forwarding user planegateway, wherein the control plane gateway is a serving control planegateway for the user equipment, and wherein the control plane gateway isconfigured to: receive the location information of the user equipmentfrom the mobility management network element; select the at least oneforwarding user plane gateway for the user equipment according to thelocation information of the user equipment; and establish, with the atleast one forwarding user plane gateway, a data forwarding tunnel fortransmitting downlink user plane data of the user equipment by:receiving a first request from the mobility management network element,wherein the first request carries routing information of a target basestation; sending a second request to the second user plane gateway,wherein the second request carries the routing information of the targetbase station; sending a third request to the third user plane gateway,wherein the third request carries routing information of the second userplane gateway; and sending a fourth request to a source user planegateway, wherein the fourth request carries routing information of thethird user plane gateway.
 12. The communication system according toclaim 11, further comprising the target base station, wherein thecontrol plane gateway is further configured to send routing informationof the second user plane gateway to the target base station via themobility management network element, and wherein the target base stationis configured to receive the routing information of the second userplane gateway via the mobility management network element.
 13. Thecommunication system according to claim 11, wherein the locationinformation of the user equipment comprises at least one tracking areaidentity (TAI).
 14. The communication system according to claim 11,wherein the location information of the user equipment comprises servingbase station information.
 15. The communication system according toclaim 11, wherein the control plane gateway is further configured tosend a create session request to a target user plane gateway for theuser equipment, wherein the create session request is to be used tocreate, on the target user plane gateway for the user equipment, abearer context for user plane data transmission, wherein each createdbearer context comprises routing information of the target user planegateway, wherein the target user plane gateway is a serving user planegateway corresponding to the location area associated with the locationinformation, and wherein the target user plane gateway is configured toreceive the create session request.
 16. A communication method,comprising: receiving, by a control plane gateway, location informationof a user equipment from a mobility management network element, whereinthe control plane gateway is a serving control plane gateway for theuser equipment, and wherein the mobility management network elementserves as a serving mobility management network element after the userequipment is moved to a location area associated with the locationinformation; selecting, by the control plane gateway, at least oneforwarding user plane gateway for the user equipment according to thelocation information of the user equipment, wherein the at least oneforwarding user plane gateway is a first user plane gateway; andestablishing, by the control plane gateway with the at least oneforwarding user plane gateway, a data forwarding tunnel for transmittingdownlink user plane data of the user equipment by: receiving, by thecontrol plane gateway, a first request from the mobility managementnetwork element, wherein the first request carries routing informationof a target base station; sending, by the control plane gateway, asecond request to the first user plane gateway, wherein the secondrequest carries the routing information of the target base station;receiving, by the first user plane gateway, the second request; andsending, by the control plane gateway, a third request to a source userplane gateway, wherein the third request carries routing information ofthe first user plane gateway.
 17. The communication method according toclaim 16, further comprising sending, by the mobility management networkelement, the location information of the user equipment to the controlplane gateway.
 18. The communication method according to claim 16,further comprising determining, by the control plane gateway accordingto the location information of the user equipment, that the userequipment has moved out of service range of the source user planegateway serving the user equipment.
 19. The communication methodaccording to claim 16, wherein the location information of the userequipment is target location information of the user equipment.
 20. Thecommunication method according to claim 16, wherein the locationinformation of the user equipment comprises a tracking area identity(TAI).
 21. The communication method according to claim 16, wherein thelocation information of the user equipment comprises serving basestation information.
 22. The communication method according to claim 16,further comprising: sending, by the control plane gateway, a createsession request to a target user plane gateway for the user equipment,wherein the create session request is to be used to create, on thetarget user plane gateway for the user equipment, a bearer context foruser plane data transmission, wherein each created bearer contextcomprises routing information of the target user plane gateway, andwherein the target user plane gateway is a serving user plane gatewaycorresponding to the location area associated with the locationinformation; and receiving, by the target user plane gateway, the createsession request.
 23. The communication method according to claim 22,further comprising: sending, by the control plane gateway, the routinginformation of the target user plane gateway to the target base stationvia the mobility management network element; and receiving, by thetarget base station, the routing information of the target user planegateway via the mobility management network element.
 24. Thecommunication method according to claim 16, further comprising: sending,by the control plane gateway, routing information of the first userplane gateway to the target base station via the mobility managementnetwork element; and receiving, by the target base station, the routinginformation of the first user plane gateway via the mobility managementnetwork element.
 25. A communication method, comprising: receiving, by acontrol plane gateway, location information of a user equipment from amobility management network element, wherein the control plane gatewayis a serving control plane gateway for the user equipment, and whereinthe mobility management network element serves as a serving mobilitymanagement network element after the user equipment is moved to alocation area associated with the location information; selecting, bythe control plane gateway, at least one forwarding user plane gatewayfor the user equipment according to the location information of the userequipment, wherein the at least one forwarding user plane gatewaycomprises a second user plane gateway and a third user plane gateway;and establishing, by the control plane gateway and the at least oneforwarding user plane gateway, a data forwarding tunnel for transmittingdownlink user plane data of the user equipment by: receiving, by thecontrol plane gateway, a first request from the mobility managementnetwork element, wherein the first request carries routing informationof a target base station of the user equipment; sending, by the controlplane gateway, a second request to the second user plane gateway,wherein the second request carries the routing information of the targetbase station; receiving, by the second user plane gateway, the secondrequest; sending, by the control plane gateway, a third request to thethird user plane gateway, wherein the third request carries routinginformation of the second user plane gateway; receiving, by the thirduser plane gateway, the third request; and sending, by the control planegateway, a fourth request to a source user plane gateway, wherein thefourth request carries d-routing information of the third user planegateway.
 26. The communication method according to claim 25, wherein thesecond user plane gateway is a serving user plane gateway selected bythe control plane gateway for the user equipment according to thelocation information of the user equipment.
 27. The communication methodaccording to claim 25, further comprising: sending, by the control planegateway, routing information of the second user plane gateway to thetarget base station via the mobility management network element; andreceiving, by the target base station, the routing information of thesecond user plane gateway via the mobility management network element.28. The communication method according to claim 25, wherein the locationinformation of the user equipment comprises a tracking area identity(TAI).
 29. The communication method according to claim 25, furthercomprising: sending, by the control plane gateway, a create sessionrequest to a target user plane gateway for the user equipment, whereinthe create session request is to be used to create, on the target userplane gateway for the user equipment, a bearer context for user planedata transmission, wherein each created bearer context comprises routinginformation of the target user plane gateway, and wherein the targetuser plane gateway is a serving user plane gateway corresponding to thelocation area associated with the location information; and receiving,by the target user plane gateway, the create session request.